I can’t help but suspect two ego-driven reasons are behind this.
1: he foresees (or his best internal intel forecasts) a GOP bloodbath in November and he doesn’t want to face the humiliation of handing “his” gavel over to a Democrat.
Or
2: he foresees an increasingly realistic prospect of being voted out of his own Congressional seat, because he’s facing an increasingly appealing Democratic challenger (Randy Bryce) in the midterms. And that would be HOWLINGLY humiliating!

I bet the “ghost of Eric Cantor” haunts him every minute of every day. Eric Cantor was a smug, swaggering GOP Congressional leader/Golden Boy too, with all kinds of upwardly-mobile perceptions and public assumptions, until he got primaried out of his seat a few years back. And now Cantor’s in a Wall Street job that pays him a king’s ransom with none of the political jungle warfare or aggravations or other “inconveniences” (like having to work with a certified moron in the White House).

Just my opinion, of course.