The Jailer already had a plan set in motion.
According to Devos, "we would have never learnt of this calamity" had Uther just gotten rid (if he could have) of his memories, which means PRIOR to WOTLK, his plan was in motion.
Fast forward a few years and we land smack dab into Shadowlands.
But going through the storyline, Revendreth anima would have been forced into the Maw anyway. Denathrius and his plan for the drought would have happened anyway.
The only thing we have changed is stopping them.
(holy crap does this mean Sylvanas is a good person? /s)
Obviously, every thing that is imprisoned wants to break out. So the jailer having a plan is not the issue, thats normal. My point is. What the hell does the helm even do, besides taking Azerothian leaders hostage and getting the PC some sick ass loot?
The only thing the Jailer has really gained, is Anduin for a supposed weapon. but in the hell does a being that is so damn powerful that it takes 4 additional beings of similar power to keep chained away, NEED WITH ANDUIN.
like really, what if Garrosh, back in MoP thought, "no you little shit, breaking the bell on your ass is not enough" walks over and slams gorehowl into his head, what then? I mean hes going to break out anyway as per Denathrius and the machine of death being broken. So why break the helm in anticipation of making a weapon out of Anduin. And possible invite people like Gnomercy the fury warrior, xSephirothx the blood elf paladin and XLegolazX the night elf hunter into your house to farm purples. You are gonna break out anyway. Why add this variable?