Isn't Lex Luthor's pathos towards Superman simply because he can't stand that there's someone better than him, his ego won't allow it? All his money, his power, his brains, isn't enough to overcome the Man of Steel, and he can't stand it. He can't stand not being at the top, he thinks Superman looks down at him, and that all the people who would normally be looking up to him are now looking at Superman instead. He can't fathom the idea that Superman is just this really pure, genuine, and simple guy because Lex himself is fundamentally different at his core. Superman isn't human and Lex is, but Superman has far more humanity. Superman works for the people which bolsters his image while Lex tries to manipulate his public image.

Simple put, Lex cannot and will not understand Superman because doing so would crush his own ego. Lex cannot let anyone else go before him, and when he does, it's part of a longer ploy to get ahead. Superman, by remaining humble, comes out ahead, not because he wants to come out ahead, but because he believes in doing the right thing.