Now that he has recused himself, the Senate needs to move on approving his deputy AG before the Obama acolyte that's the deputy now, takes charge of the investigation.
There's nothing to stop Sessions from investigating Obama for illegally-wire-tapping Trump Tower before the election. Or Hillary's email scandal. Or the Clinton Foundation scam.
But to investigate anything, there has to be some evidence that a crime was committed. You can't just go after your political enemies willy-nilly.
Whatever evidence Trump has that caused him to Tweet these allegations against Obama, may be enough but we don't know what that evidence is yet, do we?
The coup plotters must get Obama’s appointee to be acting AG so DJT is forced to fire him and we have a Saturday Night Massacre (according to the media)