The transparent partisan absurdity of Impeachment Theater is a big reason. The political impact was always about motivation, not changing anyone's mind. Trump supporters much more motivated by outrage than Dems are by these weak-tea, absurdly vague "articles of impeachment."
Trump partisans are getting reminded of why they voted for him. Everything they loathe about Democrat politics, the media, and the permanent bureaucracy is on prominent display. They're laughing uproariously at Dems pretending to be solemn and reluctant.
There isn't much comparable energy on the Dem/NeverTrump side. They heard a lot of big, big talk about bribery and treason, but it was all total B.S. What they got was "articles of impeachment" that boil down to the usual ORANGE MAN BAD stuff. It's boring as hell.
There's a palpable sense of disappointment settling over the anti-Trump side today. This isn't exciting - it's a letdown, and the more astute Dems know it's likely to hurt their side more than Trump. You can't pry a president out of the Oval Office with a wet noodle like this.
As for the people who aren't really partisans either way, this half-hearted futile impeachment effort just makes the Dems look weak, which is much worse than looking like partisan opportunists. It sends a very strong message of: "We know we can't beat Trump in 2020."
Nonpartisans tend to view politics as a horse race, and they tend to like the stronger horse, which is one reason incumbents have an edge. Impeachment Theater ended up looking like Democrat desperation, a futile effort to reverse a touchdown with nitpicky penalty calls.
Add the visceral public revulsion to what we've learned about the Bidens in Ukraine - easily understood corruption where the defense is far more complicated than the charge - and you've got a farce that demonstrably hurt the already weak Dem front-runner far more than Trump.
Much of the public dislikes seeing political campaigns turned into pseudo-court proceedings. Impeachment Theater might actually have inoculated Trump against criticisms that could have hurt him in the general election campaign. Voters will feel it's all been litigated already.
It feels like a win for Trump because it is - more of a win on points than a knockout, but it'll do. /end
