I always found it weird how stable and down-to-earth he was (compared to other ancients), and how consistent that trait was in his several incarnations we meet throughout the game. Even being trapped inside Zodiark for thousands of years didn't shake him. One would think he had some foreknowledge of what was going to unfold, but I digress.
Ultimately, Hythlodaeus had only one goal: his and his friends' return to the star. He just wanted to die and help Azem and Emet in their own goals so they can die with him. In the context of ancient society, I'm sure that's beautiful and everything, but it does sounds very grim and scary in the context of the sundered mortal world. And in the end, he did get his wish. That's why I kind of side-eye Hythlo a bit and find him suspicious, because everything essentially worked out pretty well for him.