It is not mere curiosity to want to get the facts. It should be standard operating procedure in a case with such sweeping ramifications. If the tables were turned and it was Barak Insane Obama who died and a republican judge deciding no autopsy, the left would scream. Or if it were a liberal judge... No one is harmed by getting the facts unless there really was foul play.
Your analogy makes no sense. No judge has BANNED an autopsy. The government didn’t confiscate his body and throw it into a volcano. If his family wanted an autopsy, they could easily request one.