The domestic market isn't big enough to support two massive blockbuster franchises at once, and it certainly didn't help that Paramount had no idea how to market it. Star Trek 2009 had one of the best trailers I've ever seen. Beyond's trailer made it look like a low- budget knockoff.
not to diminish star trek 2009 (i love it), but its box office was boosted by a weak slate of films that summer, not just the absence of star wars as a competitor. the notable films from that summer other than trek were x-men origins: wolverine, angels & demons, transformers: revenge of the fallen, harry potter and the half blood prince, and up. i would say only the latter two films really have legacies.
since 2009, the marketplace has changed and has become saturated with mega franchises. summer 2016 was stuffed with franchises with name brand appeal and a lot of them failed to make a dent... ghostbusters, ninja turtles, bourne, alice in wonderland... star trek beyond was a casualty of poor marketing, natural decline in interest, and its release date.
but star trek and star wars should be able to co-exist, they did before. i mean, sure DC is looking like a wannabe marvel studios right now, but both franchises are doing well. paramount just needs to accept star trek isn't star wars and adjust budgets and release dates accordingly.
star trek 2009 is still in the top 10 of paramount's highest grossing films of all time (star trek 2009 is #10, into darkness is #15), i really hope they don't kneecap themselves over star trek beyond's disappointing returns.