What investigation? There is none going on, as far as I know.
Boente may have been nominated by Obama, but Obama also changed the Justice Department protocols so that Boente would not be a successor to the U.S. Attorney General in matters like this. It was Trump who signed the executive order reversing Obama's move.
P.S. -- Boente is a political appointee, so Trump can fire him tomorrow if he wants to.
“It was Trump who signed the executive order reversing Obama’s move.”
Somehow I don’t think Trump had this scenario in mind when he did that. I believe Sessions said Boente will head any campaign related investigations. Yes Trump can fire him tomorrow but what would happen if Trump fires the person investigating any possible interference in his own election?