Thor: Ragnarok - What The Ending Really Means
10. Asgard Has Fallen
The end of the movie sees Thor realise that Ragnarok has to happen (something that echoes the comics specifically) in order to defeat Hela, who draws her power from the place. So he and Loki throw Surtur's mask into the Eternal Flame, bringing about the apocalypse and the demon destroys their home and seemingly defeats Hela.
The Asgardians are now a nomadic people and Asgard is space debris. Strictly speaking, though, thanks to the film's "the secret was inside you all along" message of positivity, Asgard hasn't fallen, because it lives on as long as its people survive as a culture and a community.
In the comics, when Ragnarok brought about the end of Asgard, Thor rebuilt it on Earth (which led to the Siege story arc), which would be an interesting way to take things. It would also be handy for future Avengers movies, should Thor survive beyond Avengers 4.