According to NPR Weekend Edition on Nov. 23, 2019, with Simon and Elving, impeachment hearings show the case against our president is "remarkably strong." Then the question concerning the "inexplicable relationship between President Trump and President Putin" comes up.
This is the answer provided: "Now most Americans regard any suggestion of their president being cozy or too cozy with Russia as unthinkable. Yet so much of what President Trump has said and done in Ukraine and Syria and with the Mueller Report serves the interests of Russian President Putin. And it's hard to find a plausible explanation for that.
"My answer? As with every other investigation on corruption, follow the money. President Trump's taxes would be a good place to start.