He already has more money than he will ever need. At this point it would just be about keeping score and raising his.
He's in a new game, and he wants to "win" this one too.
The more I think about it, and I'll stop thinking about it soon (having made up my mind), Ivanka dropping the "run Trump Properties" gig in favor of an unpaid WH gig bothers me. She's getting something out of this, and as the saying goes, "it's all about control." I don't like her having an office in the WH, not one bit. If my old man had a well run company, and I was "into it" as a manager, and my old man landed a political job, I'd stick with the paying job, if I was good enough at it and enjoyed it. I don't think Ivanka's motives are as pure as she thinks they are; and whatever impression I had about "Trump's good judgment" just took a big hit.
Trash talking the HFC in favor of the "Republican Agenda" (whatever the hell that is, we don't know until it's revealed) makes me view Trump as a typical Republican. And I don't like typical Republicans.