Ask yourself this: in the span of time that Lex had as a billionaire and household name, had he ever done anything even remotely close to the absurd feats of science and ingenuity that he'd eventually get up to as a direct result of trying to kill and/or humiliate Superman. The answer's no. Being a billionaire is impressive to the average person, but in comparison to the nonsense that he's able to do to attack Superman it's laughably underwhelming.