It isn’t that the virus outright kills them. They just typically don’t get close enough to animals that could infect them. They are prey animals so they wouldn’t approach infected animals, they would run. They are also very small so the initial bite or scratch that could infect them kills them before they actually develop the disease. But a squirrel living with a raccoon because some guy thought it was cute. Yea, that would do it
Ignoring the rabies comment, a squirrel isn’t a pet it’s a wild animal. Taking wild animals from their environment and keeping them as a pet is illegal and should be. Its is terrible the animals were killed, but it is the “owners” fault. He should have taken the squirrel to a wildlife rehabilitation so it could be returned to the wild. But instead he kept it to do tricks for him. He endangered the animals and anyone who interacted with them. This is a consequence of his actions?