Why? So many reasons:
-He's *** RICH, with a multibillion dollar corporation
-He's a genius. He wants something, he builds it. And some depictions show him capable of making really great stuff and just not capitalizing on it. If I were him, I'd cure cancer just for the cred.
-When your archnemesis is the Man of Steel, other villains listen to you. He didn't get put in charge of the Legion of Doom for nothing, son.
-He's voiced by Clancy Brown. You know you can get as much tail as you want when you're smart, rich, AND you've got a voice that turns straight guys over to the pink side.
-Nobody can put you in your place like Lex Luthor when you're
-He's got 40 cakes. 40 cakes! That's as many as 4 tens! And that's
*** awesome!