mcconnell and schumer will get together and map out the rules and what witnesses can be called, then the full senate will vote on these ruled. Trump will be constrained by the rules and witness list. I do not believe mcconnell is going to give Trump a free hand to investigate anything he wants. mcconnell would love for Trump to be removed, but there is that pesky election comming-up. That is Trump’s only advantage here, the election.
And it's not something that requires cloture - its a 51 vote rule. The man gets to try his case.
McConnell wants what is best for McConnell. He KNOWS that means to wreck the dems - even if he is saddled with Trump. He's not stupid. He knows this can be )if played right) a TRAINWRECK for the dems.
He also knows if he doesn't allow Trump to destroy the dems - it will be a trainwreck for him and he will go back to being the minority leader - which is the last thing he wants. SO - with that in mind - he will tell Chuckie to pound sand.