They are self-governing organizations of private citizens. What they want is actually all that matters when it comes to when and where they put their candidate on a stage. As corrupting as political parties can be at times, they’re still just groups of citizens who agree to field a candidate in elections. They are under no obligation to give airtime to literally anyone they don’t want to win, and so they’re under no obligation to do literally anything to help RFK Jr between now and November.