ELI5 If utlization of 2 different stocks has been nearly at 100 percent for months why is one Cost to borrow low and the other high?

First of all I do not intend to bring discussions that belong to other subreddits here, but I feel people here have a better grasp on the fundamentals and Im struggling to understand what determines Cost to borrow.

If stock A has between 95 and 100 percent utilization with barely no shares to loan during months, and stock B seems to present the same scenario how can there be more than a 80 percent difference in cost to borrow from one to the other? What drives CBT up besides the avaliability of shares?

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Thanks in advance