I didn't see the trailer but yeah you're right, there are so many trailers in recent years that completely spoil the movie they're advertising. They will keep making them like this though, because studios have done research on this and they found out that they will earn the most money if they give away things in a trailer. Apparently people are - in general - more likely to see the movie if they know what it's about. It's something like that, I'm not sure of the specifics!
But take the Terminator Genisys trailer for example. Spoiler alert:
You are literally shown the biggest twist in the movie, that John Connor has turned into a Terminator. IN THE FUCKING TRAILER! I actually liked that movie in opposition to most, but maybe that is because I saw the trailer so long before seeing the movie that I had forgotten what happened in the trailer? But yeah, people were pissed about that. And it sucks that studios will keep up this trend.