I was with you right up until you said were trying to redirect away from "Biden". I think that the Ukraine hoax may be set up in order to throw Biden under the bus. Notice that the Democrats drew attention to the Biden scandal information in the phone call even though Crowdsource was the first item mentioned by Trump.
Therefore, one could conclude that they were more protective of the origins of the Russia Hoax than Biden's scandal.
I think that if Biden doesn't survive that the Dems would be happy to run with someone from the wings. They know that the Youtube video of Biden bragging about blocking funds in order to get the Ukrainian prosecutor fired is out there. Notice that the first charge against Trump was the same type of quid pro quo. I don't think that that was a coincidence.
While you’re right that the democrats don’t want Biden as their 2020 nominee, I think that their biggest motive for the Ukraine hoax is to deflect attention from the Barr/Durham/IG investigations into the origins and perpetrators of the Russia/Trump collusion hoax.
Biden is not that important to the democrats, and the number of people that could be brought down by Barr/Durham/IG investigation, is infinitely more important to democrats. Democrats would be brought up on charges of sedition, perhaps treason too, and the people that could be brought up on charges would range from the former president to the high-ranking people in the DOJ and FBI and CIA and even in congress, and no doubt, many in the lett-wing media that assisted in perpetrating the attempted take-down of a duly elected president. Biden is but a mouse compared to the elephants that could be in very deep danger of prison time.