The Progenitor was also betting that he could live through this chaos. Besides, there was nothing left for him to lose. Even if he misjudged the situation and no one would follow him into the next dimension he stepped into, causing him to die in Su Ming's hands, then once he disappeared, everyone would know that Su Ming obtained his Nascent Divinity, and because of that, he would truly be able to shift the disaster in another direction.
This situation made it seem as if no matter what Flame Fiends' Progenitor did, Su Ming would still find it hard to not be chased down.
If Su Ming could seal him so quickly that Zhu You Cai could not save him in time and cause others to be unable to take action, then he could be considered to have destroyed this trap. But the prerequisite was that he gave the Nascent Divinity of Flame Fiends' Progenitor to someone else.