When I run a game, I focus on giving the player characters (and players) a sense of agency and creating the sense of an open world that isn't forcing them down one direction or another. This means I player initiative drives a lot of the developments in the campaign. There are other forces at work as well, but the players can always choose to go left when the world goes right. Like real people they can up and quit a given course and take another. There may be consequences for doing so, but they always have that option. But sometimes the world comes crashing down on them like a storm. Maybe it was something they unleashed, maybe it was something fated to happen from the dawn of time, but either way when these rare events occur I play the impending disaster to its fullest. In these moments there is often little they can do except brace for impact or find something even more powerful that is capable of matching the threat.