The answer to the query "why didn't Beyond do better?" can be approached objectively.
BEYOND:
7.4/10 IMDb
83% Rotten Tomatoes
68% Metacritic
STID:
7.8/10 IMDb
86% Rotten Tomatoes
72% Metacritic
ST09
8/10 IMDB
95% Rotten Tomatoes
82% Metacritic
Ergo, the film was not as well received by audiences as the previous movies.
I read a lot of subjective reasoning on this forum - especially regarding the marketing. But I see precious few figures to back up the claims.
Another objective argument could be to do with the casting. Benedict Cumberpatch was a huge draw for many, whereas Idris Elba is less well known and was hardly visible in the promotional material.
My subjective feeling for why the film failed is that it doesn't connect with the audience. It's a trite, boring tale which is predictable. The message of unity good, individuality bad was simplistic and the film lacked thrust. As a trekkie, I hope the film succeeds in China so that there are more. As a film fan, I want JJ Abrams back, his movies showed innovation and flair and his track record is flawless. How this film cost so much to make is beyond me, with TFA on a similar budget, Trek looked small scale and weak by comparison. The best thing about Beyond is the cast and the very small emotional moments, but this is cinema, not TV. Themes need to be larger, stakes higher and the story needs to be much, much better - more epic and more resonant with audiences.
It's still getting very good ratings, IMO.
Plus I am not sure if most people consult Rotten Tomatoes before they go watch a movie.