Enough is enough. Many of these candidates know they don’t have a chance to make a blip on a poll. This is about stuffing their pockets with campaign contributions.
Other motivations may apply as well, not germane to picking the pres nomination: vying for VP slot, getting issues into the debate, increasing name recognition for a future "real" run, and so on
Cut off debate participants just before Sen Cruz.
You know that’s what they’re thinking...