While the ending we saw, with half the universe being erased from existence, was certainly one of the potential endings, it was still a huge deal that the movie actually followed through with the cliffhanger ending that was going to leave fans wondering just what was going to happen for an entire year.
While many were shocked, Benedict Cumberbatch recently admitted he was thrilled by the development, because he loved seeing the film take such a risk.
The end of Avengers: Infinity War was a massive shock to the audience.