As nice as it would be to think impeachment was a selfless act, that it would be bad for the Democrats to follow through, I've never really thought that to be the case.
Frankly, the idea that it would be bad for those seeking impeachment has always struck me as a Fox/Republican/Trump narrative; that if you get enough people who want it to be true to repeat it, maybe those with the power (indeed the directive) to impeach will think twice. Maybe it worked...ish? Pelosi certainly appeared to be on the fence, but those who wanted to see Trump impeached weren't going to be swayed, and neither were those who didn't, so perhaps she was trying to appeal to those who themselves were on the fence.
The thing is...I don't really think anyone ever questioned whether Trump should be held accountable. People either want him to be held accountable or don't. The former is obvious, but the latter requires that those who seek to defend him look beyond the acts for which they don't want him to be held accountable and instead distract through attacks on those who want him held accountable and obfuscate through creative and intentionally misleading interpretation of the process. We've seen plenty of both right here, not to mention from those who ostensibly represent us in government.
A common tactic seems to be to claim that those seeking impeachment most recently have been wanting Trump gone since the beginning. Maybe that's true, but it certainly doesn't absolve him of the misdeeds that actually got him impeached. And it was so nice of him to commit those acts so brazenly and justify that supposed want.
As for Trump wanting to be impeached, I'm on the fence.
On the one hand, I genuinely don't believe he wants to be president. The lure of the bully pulpit is real, and we all know he loves the spotlight, plus there's the undeniable crony factor that ultimately benefits him and the opportunity to benefit himself, either directly or indirectly through associates, by implementing policies. And the ability to affect the market in 140 characters or less, a significant portion of them subject to caps lock, is just gravy. But the other stuff--all that responsibility--is such a burden. I don't think the other stuff is worth it to somebody like him.
When it comes to no longer being president, losing re-election is tantamount to death. It's pure failure. Completing a second and final term probably isn't so great a prospect either because it just shows he's subject to the same limitations as nearly everyone who preceded him. But impeachment? All that attention? The martyrdom without that pesky death bit? That's got to be appealing to someone who would so obviously want to go out in a blaze of glory, or, as glory seems unlikely at this point, a blaze of any kind.