I am a very remote observer of the US political scene, but it's been obvious to me that McConnell is the most powerful person in the US, because, unlike Trump, he knows how to execute on his plans (see: SCOTUS etc...).

McConnell believes impeachment push will help rid Trump from the GOP, but has not said if he will vote to convict - CNN

Another person with direct knowledge told CNN there's a reason McConnell has been silent on impeachment as other Republicans have pushed back: he's furious about last week's attack on the US Capitol by the President's supporters, even more so that Trump has shown no contrition. His silence has been deliberate as he leaves open the option of supporting impeachment.

[...]

While he knows they all aren't there with him, the Kentucky Republican believes the party needs to turn the page.
Several GOP sources said on Tuesday that if McConnell supports conviction, Trump almost certainly will be convicted by 67 senators in the impeachment trial.
"If Mitch is a yes, he's done," said one Senate GOP source who asked not to be named.

Feel the luv:

A source familiar with the relationship between the two men told CNN that McConnell is furious with Trump. The source said McConnell "hates" Trump for what he did last week following the attacks on the Capitol that left at least five people dead including a Capitol Hill police officer.

Also, speaking with a former colleague:

McConnell is also speaking with the President-elect about how the chamber should handle an impeachment trial against Trump.