I don't think that unexpected things are necessarily funny. Unexpected stupidity or weakness is funny. Unexpected cancer isn't funny. To make it funny, you have to make someone stupid.
As you could imagine, the theories have that as a core idea, but are more detailed than that. Nobody ever thought that unexpected = fun.
Among other things, there’s different level of unexpected, something that bends the laws of physics (the cartoon character suspended in the air for a while before falling down) is more funny than, say, the character speaking japanese.
To criticise a theory it might help to read it first…