I just had a hard time understanding why so many Democrats would want to jeopardize their political futures, so I said to myself, this cannot be, those people are nuts. Nah, they wouldn't really do this. I guess this is really going to play out to the stupid end. (in the end they will look stupid)
I think the calculus is pretty simple.
1) There's no real evidence of impeachment affecting most people's political futures, if anything the public is modestly in support of it.
2) There is overwhelming evidence of multiple impeachable offenses that their oaths to the Constitution require them to act on.
3) The impeachable offenses in this case specifically revolve around Trump attempting to use the presidency to rig the 2020 election in his favor. Before, the primary argument was to just let America vote him out. Now that Democrats saw he's trying to rig the election though that option becomes a lot more problematic.
Numbers 2 and 3 were immediately obvious to anyone paying attention and number 1 showed to be true pretty quickly. Regardless though even if you turn out to be 100% right that this costs some people their political futures it is a credit to them and the Democratic Party that they valued our democracy more than their own political power. It's sad that Republicans don't share their sense of duty to the country.