See Post 26 by House Atreides: the Senate is holding up confirmation of the replacement.
Trump should:
1) fire the Obama appointee and put the DoJ’s least awful career staffer in the job as Acting US Attorney for DC.
2) Make a major public issue of the Senate blocking appointments. The scumbags can’t handle any negative pressure and might get going if the spotlight was on them.
That sounds like our best hope. Schumer can't be counted on to have a sense of shame, but McC might care about negative publicity. However, sometimes the senate acts as if the Ds are in the majority. For one thing, how many "GOP" senators really want Trump to fail?