It is an hard question.
He didn’t win the election, and it is unlikely it was rigged.
So does Trump believe what he is saying?
Or is he saying it to hide his embarrassment about losing and doesn’t believe it?
There isn’t really any credible evidence that it was rigged. There are things being said that have no evidence to back them up. Trump and his supporters are using that.
Is Trump mad? - Probably not.
Is he bad? - Probably.
So, calling him a fruitcake lets him off the hook. He is dangerous and needs stopping, but he needs to go to prison, not the looney bin.