I can see what you're saying, but take a moment to consider his rap sheet. He's got multiple counts of theft, robbery, aggravated assault, public indecency, attempted murder, and releases more methane into the atmosphere than a herd of cows. Sounds like a pretty bad guy to me. Not the sort of guy you'd want to find yourself alone with in a dark alley.
Also, I found an interesting little tidbit from his Wikipedia page: "The name "Wario" is a
portmanteau of "Mario" with the Japanese adjective
warui (悪い) meaning "bad"; hence, a "bad Mario" (further symbolized by the "W" on his hat, an upside down "M"). Official Nintendo lore states that Wario was a childhood rival to Mario and
Luigi who became jealous of their success." Basically, he was created with the intent of being a dark reflection of Mario like Reverse Flash would be to Flash, or Venom to Spiderman (the comic version, not the Tom Hardy one).