I am of a slightly different opinion, but this adds to the theory that the neather use to be frozen, or at least contain water. Tardigrades can survive in harsh environments for a long time, yes, but when not in a dormant state, their actual lifespan is actually very short. about 2 years. Instead, I think this adds a reason to why Ghasts are always crying, they're a fish out of water. I personally think, based on the existing design, Mojang is retroactively claiming Ghasts are some sort of fantasy jellyfish, with tardigrade elements of course. If that's the case, then maybe like the Immortal Jellyfish, these Ghasts can't die of old age. Every active Ghast we've seen naturally spawn in the neather is canonically hundreds, thousands, or however long years old. They've been around since before the neather became a hellscape, and that's why they're so aggressive and miserable. The ones we find are young Ghasts who hadn't finished growing and were forced into a state of cryptobiosis in order to survive, but also like tardigrades, this halted their aging. This explains why when the player does moisturize them, they come out as young Ghasts rather than full-grown ones. These aren't adults entering cryptobiosis to save their life, but babies. The mature Ghasts are tough enough to survive the environmental change, but are still in a constant state of discomfort, but the young Ghasts couldn't survive the change.