It's really hard to run through all the possibilities.
There are a couple of very concerning recent developments: The McRaven op-ed (and the fact that he wasn't arrested for UCMJ violation), the McConnell freakout over Syria, and the John Thune comments on how concerning the evidence (which he has not even seen) is.
This leads me to think that they may be plotting a lightning removal - Roberts calls the Senate to order, rules all defense requests out of order, allows McConnell to move to secret session, and Trump is out by teatime.
Something sure has changed in the past few weeks.
I think it was the Syria pullout. Qatar put up big money to get their gas pipeline built through Northern Syria - with the US military serving as mercenary guards. I think a lot of GOP Senators have been reminded that the contents of their Swiss bank accounts could become the subject of public discussion if they didn’t do something about this interloper Trump, and fast. So if standing up for Trump comes at such a huge price, maybe President Pence wouldn’t be so bad, after all...