This isn't really relevant to the current investigation. Even if you take those comments as factual, by "taking down everybody" he meant forcefully rebuking the Republican Party for not supporting him through the turbulence. He would've turned his voters against the other republicans on ballots which would've sunk their chances in their own races...
But then you have people saying if he goes down due to Mueller he's going to take everyone with him. Outside of his administration.....who? And why would he target republicans when it's a largely democrat pool of investigators conducting the probe. If he goes down, republicans will be running from him, and it's a guy who has spent a single year in Washington.
The hyperbole in these tweets is fantasy....it's tough to take it seriously.