These are not examples of power for it's own sake, in your first example it is because it grants them the warm and fuzzy feeling of people fawning over you, and in the later it is having people kowtow to you. You probably can't drill down into their motivations any further, as at some point the answer just becomes, because it make (figuratively speaking) areas of brain light up, and the wiring of the brain is just something which is super mysterious to us right now.
It also doesn't have to lead to morally grey antagonists. Just because group X shat on the antagonist from a great height when they were growing up, doesn't justify whatever terrible things that the antagonist does to them when the roles are reversed. You can understand someone's motivations and still think they are a massive piece of shit.
I do agree that Seymour is looking less and less likely to be the master chess player, but who knows?