Some people are billing this Avengers: Infinity War Super Bowl spot as a “trailer” but really it’s just a teaser whose message is, simply, “EVERYBODY’S IN THIS MOVIE.”
It’s like: “this is the one you’ve been waiting for, kiddos, it’s what we were all building towards. Spider-Man, Guardians of the Galaxy, Dr. Strange, the Winter Soldier…we’re going to find a way to shoehorn everybody in.”
It sort of is what it is; the big-budget equivalent of a comic book crossover in the grand “Secret Wars” style. With a big purple CGI Josh Brolin at the end.