To fix it quickly you are going to have to abuse your power immediately like Republicans have. But you are also going to need at minimum a majority in the house and Senate, preferably a supermajority which I doubt that happens.

Prosecute traitors immediately.

Immediately expand the supreme court

Help install safeguards so this never happens again. Like for presidential nominess for secretary of defense or education. Only select people who work in that field and with knowledge of the job can nominate people for consideration and the president can only hire those nominated