Why was the Rebel base on Crait abandoned?

Question

In TLJ, the remnants of the Resistance fleet head for what Leia says is an abandoned Rebel base on Crait.

Why was the rebel base on Crait abandoned?

• Had it been discovered by the Empire?
• Was it too small, too remote, or too inhospitable to be worth keeping?
• Did the Rebels regularly abandon bases as a security measure, sort of like changing your password every six months? Considering that the Rebel base on Dantooine had apparently been abandoned for some time before its discovery by the Empire (in ANH), it seems plausible that regular base rotation is a standard Rebel practice, but it seems awfully expensive.

Answer 1

The film's Visual Dictionary indicates that during the Rebellion Era the base's security was compromised, hence their decision to abandon it.

BASE DEFENCES

The Rebellion hastily abandoned Crait during the base's construction when a traitorous ally alerted an elite Imperial unit, SCAR Squadron, to their location. The rebels left behind their Spiezoc v-120 and v-232 artillery emplacements.

Since Crait had no discernible value, Leia anticipates (correctly) that that planet isn't likely to appear on the First Order's star charts.