This seems like a really slanted explanation that largely overlooks the lead up to the events you mentioned. First, the parties have always tried to out maneuve

This seems like a really slanted explanation that largely overlooks the lead up to the events you mentioned. First, the parties have always tried to out maneuver eachother. Things like judge appointment might be departures from a specific norm but they're not a departure from the broader trend of exploring the system for pressure points that can be leveraged into comprehensive strategies. The US isn't the UK or a lot of Europe, agents of the system frequently depart from established norms because those norms are just gentleman's agreements like you said and not things important to the system like the various ways the queen routinely waives chances to exercise her various reserve powers. The concern was much more simply that being viewed as ungentlemanly could backfire but that quit mattering as much after Trump ran basically all of his 2016 campaign on the image of being a rude crude anti-Bernie who'd whip DC into shape (lots of people viewed these two as the wild card candidates for some reason even though they were very different). And the impeachment itself was fought by many influential Democrats, including Pelosi, precisely because they knew it would fail and were concerned the loss would motivate opposition voters while damaging the 2020 turnout of Democrats who might see it as a sign that the party was still largely impotent or simply disorganized. Just because Pelosi prefers to drive the car doesn't mean she likes the destination. She was criticized often beforehand for fighting the idea of an impeachment. She probably just realized that the topic wasnt going away after all, so presenting a unified front was better a better option than letting the infighting go on damaging the party's optics. But now the impeachment is largely viewed as just another in a series of fishing expeditions (to people in states that don't reliably vote for one party or the other) and on top of that the progressives in the party are currently demoralized that their candidate is an establishment figure rather than someone more extreme like they'd been hoping for. It arguably would have been no worse if they'd just bided their time and focused on dominating the 2020 media landscape with a flurry simultaneous actions. This could have been used to eclipse media narratives like Biden compromising #MeToo's integrity or the association between the Dems and staying locked down (Americans are rapidly developing lockdown fatigue). But instead the Dems are going into an election against an incumbant President with no compelling parries left, most vocal elements of the party exhausted, and a press that (outside historically sympathetic outlets like CNN and WaPo) has lost its original interest in party mascots like AOC who could have been useful in 2020 to motivate the youth and progressive votes following the defeats of Yang and Bernie.