You're confusing "conspiracy" with "mystery" or maybe "fantasy".

A conspiracy is any two people planning a criminal act.

Area 51 or moon landings or UFOs or alien lizard people, these are not
"conspiracies". They are fantasies; there is no data. It's like me
making a theory about an invisible monster standing right behind you.

The problem with using "conspiracy theory" as an insult is that it
makes it harder to discuss real conspiracies as people insist in
discussing Area 51 or whatever.