Everyone calm down. While we don’t know why witnesses weren’t called, we know that the Democrats didn’t “cave.” They’re not hapless idiots. They’re savvy fighters, and they must have had a damn good reason for this. Stop blindly attacking them and let this play out.
For instance, the Washington DC Attorney General let it be known last night that he’s looking to criminally charge Trump for the insurrection. That’s infinitely more important than impeachment. Perhaps he asked the Democrats not to screw up his prosecution by calling his witnesses.
It’s also possible that one or more of the witnesses changed their story, and therefore it would have backfired. There are all kinds of plausible explanations for what just happened. “Democrats stupidly caved” is NOT one of them, because these Democrats are NOT stupid or cavers.