Asgard before Midgard

These being said and keeping in mind that Loki is now on the throne, what else could be said about Thor Ragnarok?

Asgard is basically the protector of Earth, and not just because of Thor's love for Jane Foster. As seen in the first Thor film, a giant battle was thought to prevent the descent of Earth into a new ice age of sorts.

So for Thanos to actually threaten Earth, he must first defeat Asgard. And having Loki on the throne makes sense in an absolute way. After all, Loki was brought back to life (or whatever) because of Thanos. His army from the first Avengers film was also provided by Thanos. So the Mad Titan still manipulating Loki isn't such an out there idea.

So Asgard must fall before it's Midgard's turn. We do believe that this is the importance about which Kevin Feige talked about. This is the cosmic event that will trigger the Infinity War