I think after his exposure on SNL last night, which was almost entirely positive IMO, he would not serve his own interest by attacking Ben at this point. His better course of action will be to work on convincing Ben’s supporters to embrace his message and agenda for when Ben inevitably drops out. It seems very likely that Trump is going to be the nominee. I know Democrats that are crossing over for him. His message is resonating like an idea whose time has finally come.
Yes, Carson is imploding all by himself without any nudge from Trump. As they say, never try to interfere when a enemy (or in this case a competitor) is committing suicide.