Desperation makes people (or groups) do desperate things. The GOP - despite controlling the House, Senate, and Executive branch - sense that their window of opportunity is limited, due to their gross incompetence and galling self-interest. They can't help themselves in that latter aspect, but they're not even being remotely clever about it.
With tRump, they have the equivalent of that drunk rowdy friend who does all the outrageous things that make their own transgressions look tame by comparison. With the Mueller investigation already bearing fruit (and the revelation that he's subpoenaed tRump's financial records from money-laundering Deutche Bank), the writing is on the wall. By mid 2018, we could have an appointed president (ala Gerald Ford), and that's a scary unknown for the Republicans.