Briefly, I see this as a possibly bipartisan effort to corral Trump, who has talking about getting along better with Russia--including in the Middle East. This issue of Ukraine aid/corruption has been going on most of the summer behind the scenes, with most of the Estabishment opposing Trump. Specifically, WSJ is talking about Bolton's involvement as well as senators involved.
So there's a couple of different but related angles of attack. Now, add in the removal of Coats and Sue Gordon, who would have been at the center of this, and the firing of Bolton. So, there's policy stuff, and there's also the effort to save Biden, who would be Establishment friendly.
Trump put a stop on the aid for two reasons: he wanted the Euros to give more, too, and he was concerned about the overall issue of corruption in Ukraine. There was nothing wrong with stopping the aid in that context. What I'm pretty sure is also going on is that Trump is getting good advice from Bill Barr on the legal ground. He probably should have had Barr at his side from the start of this, but the guy's got his hands full at the DoJ swamp.
What we seem to be seeing is another coup attempt, but a weaker one.