Trump is deferring to the Congressional GOP because of the midterms. They don’t want direct confrontation with him lest the their base notice the GOP is playing for Team Kenya.
Trump will fire Mueller after the midterms and dare the GOP to impeach him. They won’t because that would rip their cover away and be the end of the Party of Lincoln.
Repub leadership does not care if that happens because they have always been Uniparty. they know it hurts conservative repubs way more than themselves.