Rightfully

"This was the very first case of Heat Death. The balance of the universe had been thrown into an imbalance with Gama energy being used in a way it shouldn't be… Because the life force of mortals were being forcefully extended, that usable energy wasn't being recycled into the reincarnation cycle like it should. As a result, it was very quickly becoming unusable as more and more cultivators came into being…

"Once energy becomes unusable, it's impossible to revert it back to its original form. As a result, the fate of a universe that accumulates too much of this energy is only death. It's doomed to collapse in on itself, erasing itself from existence.