Fat Donnie still thinks the fix is in. First, he tried to keep the House from getting hold of any evidence or testimony. The willingness of long time non-partisan government employees put the kibosh on that. He probably asked Mulvaney if he could stop their testimony by having the Secret Service arrest them and lock them up.
Now he's blowing impeachment off as no big deal. He's about to find it is a big deal, and it will be forever linked with his name. Turtleman has probably assured him that any vote will be done by roll call, and that assures an acquittal, because a Repug senator is willing to sell their soul rather than face the wrath of Trump's "base."
Moscow Mitch has probably assured him that there's no way the Senate will remove him. That's not absolutely certain, however, if five Republicans join the Democrats in calling for a secret ballot. I think that's one of the reasons Mitch wants to cut the Dems out of the process of establishing the rules for the trial.
Trump probably thinks that even if the Senate votes against him, he's got a firewall in the SCOTUS, which has a conservative majority, with two justices being his appointees. I guess nobody has told him that there's no appeal from a decision by the Senate to remove him. If they vote to against him, he's gone. Get your ass out of the People's House, and take your grifter children and Melania's ugly Christmas trees (which are all white, just like his supporters) with you.
BTW, you might stop for moment once you're through the WH gate so you can be served with criminal indictments and civil complaints. Take a pair of clean underpants you can wear when SDNY locks you up.
This is all a fantasy, of course. There are too many uncertainties involved, the primary one being the secret vote. Once a senator knows he can tap dance around that, they might be willing to vote with the Constitution.
Stay tuned, boys and girls. It's about to get interesting. As Rachel says, "Watch this space."