But Ryan is one of the Good Guys, regardless.
Why did he quit?
Yes, he DOES have children, and he married well--he doesn't need the income. And of course, he also doesn't need the crapola that he has to take with that job.
But I think there's more. I think Paul Ryan sees The War that's coming. At bottom, it is a culture war, and Ryan doesn't want to be part of it. The culture that existed in the USA until (say) 1960 has been disappearing in bits and bites--and now chunks--since the Warren Court's hegemony and it ain't going to come back without a fierce struggle.
Some say it may be a bloody struggle; others hope that it will be bruising, but not worse.
Politics are downstream from culture and culture--at root--is downstream from cult: what you worship. Ryan is a politician, not a cult guru, nor really a 'culture' warrior. Ryan knows what side of that war he is really on (it's the right side, folks), but the battlefield will not be in the House or Senate.
This war will certainly weaken the US and might lead to dramatic and not-very-pleasant geopolitical consequences.
I don't blame him.