15Wario is a crazy Mario fan
A theory posed by "RenaKunisaki" reads as follows: "Mario is a celebrity, and Wario is the stereotypical creepy overzealous not-quite-sane stalker fan." Several pieces of evidence are mentioned to prove the theory. Mario is certainly a celebrity, as he has (seemingly) saved Princess Peach and the Mushroom
Kingdom numerous times. Wario wears the same exact outfit as Mario, just with yellow and purple as the dominant colors vs. Mario's red and blue. Who's to say "Wario" is even his real name and not just a nickname he gave himself, inverting the "M" in Mario? In Japanese, Wario roughly translates to "bad Mario."
In Super Mario Land 2: 6 Golden Coins (1992), Wario lives in a giant castle on an island, which has a giant statue of Mario. It is revealed that Wario stole this castle from Mario, and he is the final boss in the game. He could have been trying to live Mario's life because of his obsession with him, and built a statue for him. When Wario losses to Mario, he can't accept his failure and jumps off the roof of the castle.