There are very few things that Donald Trump actually cares about, but top on his lists is making sure that Putin, Russia, and the Russian oligarchy are treated very nicely. This is actually pretty good evidence that Trump and Russia conspired to make Trump president, and now it is time for quid pro quo - payoff.
There are more than one grounds for impeachment of this strange presidential choice, and conspiracy with a hostile foreign power is one of them. Strange that this man, who keeps telling us all how intelligent he is, periodically does Putin's bidding.
He is the biggest witness against himself.