While I certainly agree with the sentiment expressed in your post, I think this issue is much more complicated than we imagine.
Trump could have taken strong action at many points in the recent past but must have thought there was good reason not to do so. That might include the fact he has been advised that for certain actions he may take that would ordinarily be available to him, there are enough RINO's to ensure impeachment and conviction. Hat tip to Desert Rhino upthread.
Based on the Nazi SS behavior we witnessed yesterday, the "swamp/establishment" has no fear and little regard for the principles of justice our nation has honored in its past. Your first-year law student might not make it up the stairs at the entrance to the courthouse.
That may account for Trump's obvious anger, frustration and scathing rebuke of Sessions on national tv; it being an attempt to shame Sessions into resigning. Certainly, there is no reason now to believe Trump and Sessions were ever a tag-team.
Smart money would bet Sessions is in a very tight vise. Worse for our country, Trump may also be in a very tight vise with very few options.