So a few things come to mind for the finale. But i think the biggest thing for me would be that syd is the cause of all of this.
Syd kidnaps david from a different universe thinking he will share the same fate as her david. Shadow king finds a way to get to future syd and speak with her. Syd puts the delusion of david ending the world into shadow kings mind. Shadow king uses this knowledge to turn everyone against david.
Interested to see where they take this in season 3.