I know that this is an old question, but I looked through the answers and the comments here and I noticed that no one has yet mentioned any relevant information from the novelization (not even those posted since the novelization was published), which I think provides the most sufficient answer to this question; and since none of the extant answers have been accepted by the user who asked the question, I thought that I would make a contribution. (Given the length that this answer ended up being, I decided to provide a TL;DR version at the end for those who don't have the time for the long version.)
Let me start by providing some background information: I believe that it's worth noting that, during the evacuation, they were in the process of siphoning their reserve fuel and extracting other supplies for their escape, and implementing other important procedures, but this was all interrupted by the arrival of the First Order fleet.
In the novelization, Lieutenant Connix is speaking to protocol droid PZ-4CO, who alerts her of the incoming First Order fleet. Connix then asks the droid what still needs to be done.
PZ-4CO: Approximately thirty percent of the deep fuel reservoir remains to be siphoned... Scuttle procedure for mission-critical computers is incomplete. And maintenance stocks are still being transferred from lower-level stores.
Flight Officer Jones: There are still thirty pallets of cannon shells in C bunker.
p.25; Star Wars: The Last Jedi by Jason Fry
It's also noted that the ships that came to evacuate the Resistance base on D'Qar were already low on fuel when they arrived, but the process of siphoning out their reservoirs would take too long to be of any use (PZ-4CO said that it would take approximately 90 minutes to fully complete the evacuation procedures). Connix gave an order to siphon what they could and be airborne in ten minutes.
The fact that they were in a hurry to finish the evacuation was also hinted at in the film (much more briefly) during the opening scene:
Resistance Evacuation Officer: We're not clear yet. There are still 30 pallets of cannon shells in C bunker.
Lieutenant Connix: Forget the munitions, there's no time. Just get everyone on the transports.
[Star Destroyers appear]
Lieutenant Connix: Oh, no.
Which is why later, shortly after leaving hyperspace when they realized that the First Order had somehow followed them, they were too low on fuel to risk making another hyperspace jump, a move which would have exhausted their remaining supply at the time.
The fact that their evacuation procedures were interrupted, and the fact that they were caught off-guard by the sudden reappearance of the First Order fleet, meant that they were ill-prepared for this situation and that their only viable option at the time was to attempt to outrun them for as long as possible at sub-light speeds. In doing this, it was only a matter of time before each of the Resistance ships ran out of fuel, and their best chances for survival was to transfer survivors to the Raddus (which had the most fuel) from the other ships before they ran out.
Assuming that the kamikaze attack was a move that anyone considered early on, it most certainly wasn't an option until the ship making the maneuver was empty of all survivors (other than the pilot), as it would obviously be fatal for everyone on board. And it appeared that the two smaller surviving ships, the Ninka and the Anodyne (the Vigil was destroyed in the battle that came immediately after the First Order coming out of hyperspace to chase the Resistance fleet), ran out of fuel shortly after evacuating, so it was likely never an option for either of them to pull it off. In fact, it's entirely possible that the Ninka and Anodyne were already too low on fuel to even attempt this move by the time they started to evacuate their survivors over to the Raddus.
So, if this maneuver was ever considered prior to their arrival at Crait, the Raddus was likely the only ship that could pull it off successfully just based on how much fuel they all had. As we saw in the film, despite trying to outrun the First Order for many hours, the Raddus still had enough fuel to make one last jump (and the plan was originally for Holdo to simply lead the First Order away from Crait, rather than attempt to make a counterattack). The film indicates that her kamikaze attack was likely a last-ditch effort that she came up with on the fly shortly after she realized that their escape plan had been compromised. This is confirmed in the novelization:
Aboard the Raddus, a stunned Holdo could only watch as another transport exploded.
Holdo choked back a dismayed cry. She had to do something. But what? There was no way the Raddus could defend the transports -- they had moved beyond the protection of its shields.
She looked helplessly at her console, searching for some answer that eluded her. There was nothing.
A light blinked on the interface with the navicomputer.
Holdo called up the interface to dismiss whatever the alert was -- it would only distract her while she tried to think -- then paused.
Someone had entered hyperspace coordinates into the system, calculating a jump that had never been made. The navicomputer was asking if the coordinates should be purged.
It was Dameron, she realized -- he'd rushed to the bridge as part of the plan he'd concocted, the one she'd correctly dismissed as too reckless and desperate to succeed.
Holdo called the coordinates up on her console. The Mon Calamari cruiser had kept traveling along its heading for Crait since the coordinates had been entered into the navicomputer. As a result, the entry point for the hyperspace jump Poe had calculated was now behind the Raddus, on the other side of the First Order fleet.
Holdo stared at her screen, trying to figure out what she had missed and concluded that her wild hope might not be completely unfounded.
p.231-232; Star Wars: The Last Jedi by Jason Fry
Further, the novelization indicates that Holdo could not actually rush the maneuver, and had to pace her moves carefully and time it right in order for it to succeed:
Aboard the Raddus, Holdo hastily rechecked that the heavy cruiser's navicomputer hasn't kicked back the overrides that she'd had to program into it.
The First Order flagship began to slide across space ahead of the Raddus... Turbolaser fire continued to lance out from its bow, destroying the Resistance transports seekng safety on Crait.
Holdo reminded herself that there was only one way to help the evacuees -- if she attracted the First Order's attention too early, her desperate gambit would come to nothing. The only thing she could do was wait.
p.247; Star Wars: The Last Jedi by Jason Fry
She got the time that she needed. The First Order officers observing the situation noticed that the Raddus was turning. First Order officer Captain Peavey considered the possibility that she may have been trying to stage a counterattack, but didn't consider the ship to be a threat, as the Raddus's weaponry wasn't strong enough to damage the Supremacy. They quickly realized that she was actually preparing to jump to hyperspace; but, like General Hux, they dismissed it as just a futile attempt to distract them from the escaping transports. They initially decided to let it make the jump to hyperspace, figuring that they could take care of it later (and the Raddus was still far enough away to be out of the effective range of the Supremacy's cannons against its shields). Both the novelization and the film show that Hux and the other officers didn't realize their grave mistake until it was too late.
And here's where arguably the key aspect to Holdo's gambit being successful comes into play: that being the Raddus's experimental shields:
The Raddus' key strength is its advanced deflector shield system that can push the envelope of protective energy far from its hull.
p.10; Star Wars: The Last Jedi: The Visual Dictionary
This is also mentioned in the Incredible Cross-Sections book for The Last Jedi:
Raised Shields: The advanced deflector shields that cocoon the Raddus are an experimental design, capable of sustaining huge amounts of damage before failing. Though the heavy pummeling by the First Order makes structural damage inevitable, most other ships would have been destroyed long before this point.
p.8; Star Wars: The Last Jedi: Incredible Cross Sections
(Lest anyone think that this was a retcon done to explain "plot holes" or to deflect criticism of the film, the Incredible Cross-Sections book and The Visual Dictionary for The Last Jedi were both published on December 15, 2017, the same day as the film's release.)
These shields played a crucial role in how effective and devastating the lightspeed ramming ended up being against the Supremacy.
When the heavy cruiser plowed into the Supremacy's broad flying wing, the force of the impact was at least three orders of magnitude greater than anything the Raddus's inertial dampeners were rated to handle. The protective field they generated failed immediately, but the heavy cruiser's augmented experimental shields remained intact for a moment longer before the unimaginable force of the impact converted the Raddus into a column of plasma that consumed itself.
However, the Raddus had also accelerated to nearly the speed of light at the point of that catastrophic impact -- and the column of plasma it became was hotter than a sun and intensely magnetized. This plasma was then hurled into hyperspace along a tunnel opened by the null quantum-field generator -- a tunnel that collapsed as quickly as it had been opened.
Both the column of plasma and the hyperspace tunnel were gone in far less than an eyeblink, but that was long enough to rip through the Supremacy's hull from bow to stern, tear a ragged hole in a string of Star Destroyers flying in formation with it, and finally wink out of existence in empty space thousands of kilometers beyond the First Order task force.
p.251-252; Star Wars: The Last Jedi by Jason Fry
Given the desperate situation that they were in, which was already bad from the start and was only getting worse by the minute, it's unlikely that anyone ever considered this move earlier in the events of the film. In fact, I was unable to find any information that indicates that anyone had considered trying this move prior to the moment that Holdo executes it, and that she only came up with it on the fly when it became clear that their escape plan had been compromised; and even if anyone did consider it prior to that point, it simply wasn't an option until any vessel that would have been used for this purpose had at least been evacuated (and even then, it still would have needed enough fuel to execute a hyperspace jump, which the Ninka and Anodyne clearly lacked compared to the Raddus). And ultimately, thanks to its advanced experimental deflector shields, the Raddus was the only ship in the Resistance fleet that could have been used to execute this move and achieve the results that we witnessed on film.
Executing this move earlier simply wasn't an option.