In the 23rd episode of the second season of Star Trek: Enterprise, a couple of Borg drones are allowed to regenerate. Assimilation ensues. Why did they start assimilating things instead of becoming individuals just like every other drone that was disconnected from the Collective before and after the Battle of Sector 001 (First Contact)?
Hugh was liberated before the Battle of Sector 001, and he eventually accepted having become an individual. Picard was liberated before the Battle of Sector 001, and he immediately went back to being an individual. Seven of Nine was liberated after the Battle of Sector 001, and she showed no hints as to having a pre-programmed directive to assimilate things that had to be overwritten before becoming an individual. Seven was also severed from the Collective earlier (presumably before the Battle of Sector 001), along with three other drones when they were stranded and forced to go camping to survive. All of them reverted to individuals before being forcibly rejoined and recovered by the Collective.
My best guess is that something in the wreckage of the sphere was continually broadcasting a directive unique to the circumstance, but I'm looking for something a little more specific than that for an answer. I'm also looking for an in-universe answer, and not "because the script demanded it."