That was the implication I got from the flow of the narrative, Minato was a deus ex machina. Honestly, it still makes sense that he could have sealed Kurama, he had enough chakra to revive the entire village and was prepared for this very moment. With information we have from the final war (and power inflation of course) then no. Kurama should be able to bomb his way out, but if we’re strictly talking about narrative then I think Pain would definitely win if Minato wasn’t interfering.