Most of that was Playmates' fault. They flooded the market with too much product all at once and retailers were left with tons of stuff that stopped selling after Star Trek XI was released. Combined with customer dissatisfaction with most of the toyline, it's little wonder that flopped.
But that was back in 2010. Six years later, Trek is still perceived as something that really doesn't deserve a toyline as a result of that. Only Funko showed an interest in doing something from Beyond, and that was in the form of their exaggerated POP! figures.
In all honesty, I've read that reasoning elsewhere and I don't really buy it. The first (and only) wave released didn't even have a complete crew, and only one bad guy (nero) 2 playsets (bridge and transporter) The Enterprise, and 3 role play accessories. Not a huge wave considering other lines. and the quality of the toys was no worse than other mass produced Walmart peg toys. (look at the quality of "The Force Awakens" micromachines that recently came out....they are terrible....the playsets are terrible....yet they fly off the shelf because they are Star Wars and Star Wars is cool to kids right now. ) If you took a 1990s kid and brought them forward in time and showed them this toy line, they would have liked it......If you took a 2009 Kid back to 1995 and showed them the Trek Toys back then... I promise you they would have thought they were Lame. Trek Toys had their time in the sun....it passed in the late 1990s. I hate it too....but it's the truth.