When it’s only an offer from the Russian side?

there are signal intercepts incriminating Trump, emails incriminating Trump, phone conversations incriminating Trump, .... important to remember Flynn was being investigated along while before the election, Manafort too, so they were already under surveillance when they joined the Trump campaign.

We wish we knew all the Mueller knows, but that won't ever happen given how much of this is classified intelligence.

This is so yuuge (sp intentional) that it won't be possible to hide the incriminating stuff completely. When the indictments / impeachment charges begin to get to the core of this, enough stuff will come out to convince everybody except the 15% hardcore nutzo Trumpanzee base.

Courage.

Completely humiliate him or better still, do it while arresting Mike Pence and Mitch MeConnell.

Show of force.