The cerebellum contains more neurons than the entire rest of the brain combined, yet losing it leaves someone alive, aware and merely clumsy. What does that mismatch tell you?

A. That neuron count measures precision needed, not how essential it is

Size buys precision, not indispensability. Coordinating movement in real time is a vast computation and the body limps on without it; running respiration is a small computation with no substitute at all. What a lesion costs depends on whether anything else can do the job.