I see a slightly more insidious motive for Trump. This may be a stretch but here I go. Hillary was mortally wounded in the IG report. It is over for her. The Democrat party will not allow bernie to be the nominee. He is anti their establishment and he will get slaughtered by Trump. The Party will give her the nomination but she will resign based on poor health and her “grand child” needs her. Obama will grant her pre indictment clemency . Since the convention has been held, there will be a special “closed” convention of State “designates”. No press or cameras!! . Bernie will go wild but the nominee will shock you. Trump wants to build up bernie as much as he can to accentuate this trickery on bernie and infuriate his communist followers. The “debate” will be fun to watch . Trump will bait bernie on how he has been screwed. Its all a plan.
I’ve got my fingers crossed for a Trump vs. Biden vs. Sanders ballot in November. That’s my call.