Crumbling Buildings
This is a detail that is right out in the open but may not be picked up by those who decided to skip out on What If. Back in the episode titled What If Doctor Strange Lost His Heart Instead of His Hands, we see very similar imagery late in the episode. Long story short, Strange destroys the universe by time traveling and interfering with fate when he tries to save his love, Christine, from dying in a car accident.
As the universe starts to fall apart in What If, we see a very similar occurrence of buildings starting to crumble upwards into the sky. What we see in the trailer is almost a one-for-one recreation of what we see in What if when the universe is on the brink of collapse.
This new trailer and the original certainly painted the idea that the situation in Multiverse of Madness is extremely dire. Although the stakes in both trailers have seemed fairly high, there’s no indication that these similar visuals mean a universe-threatening situation is at hand.