We know only some of what led them to this point, and the same would go for themselves. Granted, there's likely much they would rather keep from our awareness as well, while they scramble to make sense of the changes that have happened.

We can surmise, for example, that the presence outside of the barrier and responsible for the current state of the outside is that of the "Crawling one". The "Winged Lord" had long fallen, but these forces were opposites in some way. And then... a reminder of balance, even there. Perhaps with some investigative work, you'll find some of your own conclusions as well.