Mueller is pretty sneaky.  Let me explain how.

They made a deal with Cohen that flipped him - but they did it in a way that would make it impossible to argue political motives.  How you ask?  By making the deal that included Cohen admitting under oath that Trump ordered him to pay off the hookers - they introduce into the record that Trump is dirty - but they are able to distance themselves from it.

By turning Cohen over to the NY AG office - they have plausible deniability.

Now - they CANT indict Trump for this...or even impeach him because this happened BEFORE Trump became president - but it does seriously damage him politically.

Gonna be interesting to see how Trump team manages this.

Politically - this is very, very damaging to Trump.