There is common incorrect usage of the term "conspiracy theory". A conspiracy is a plot among multiple people to commit a crime. Fleeing to Argentina would not have been a crime, thus it could NOT be a conspiracy theory for Hitler to have fled to Argentina. There are people in the majority of legal jurisdictions in the Western World specifically in prison for conspiracies. So conspiracy theorists as police detectives are common. Convictions for people for doing conspiracies are quite common. People  being in prison for conspiracy is common.

So while conspiracies are common, Hitler fleeing to Argentina cannot be one of them, by definition.