Once Mueller ends his investigation he can’t cry obstruction of justice if DoJ goes after him.
There is no need to fire him.
IMO Mueller is stalling for that very reason and I’m betting that the democrats want Mueller fired so they can scream obstruction of justice.
President Trump knows what he’s doing.
This is why Mueller may try to stall for YEARS.... as long as he pretends to have an open investigation he tries to postpone any Day of Reckoning for his own team.
Of course, at some point the DOJ/AG may finally come down hard on him.