Taking care of an animal is a huge responsibility for a kid, especially when that animal hates the kid's guts.
Here's a video of a dumb kid who tried to convince his irresponsible mom to let him keep what may be THE biggest squirrel ever. But after the squirrel bit the kid's finger he immediately went from being a responsible pet owner to 'panicked momma's boy crying about getting rabies'. He probably should have
known that picking up a half conscious squirrel was a dumb idea but furry, cartoonishly cute animals can make even the smartest people do the dumbest things (which is why I spent half my last paycheck on toys for my cat).
I honestly doubt that fat squirrel had rabies. I think it was probably just in a food coma, since I've always considered squirrels to be the hobos of the animal kingdom. They're nice to you as long as you give them something, just be sure not to make eye contact.