The only measure of popularity that matters in this case is the popularity of the previous films, not the shows, since in order to make a profit on a Trek film, the bulk of it audience needs to consist of casual viewers who aren't fans of the shows. TMP actually did pretty well at the box office (over 140% the worldwide gross of TWOK, though a smaller opening-weekend performance in the US), but it cost a bundle to make, so Paramount wanted a cheaper sequel (and in fact TWOK was originally going to be a TV movie, which was why a TV producer was hired to make it). Once Harve Bennett proved he could make a successful Trek sequel on a TV-movie budget, Paramount wanted to continue in that vein. And as subsequent sequels did unevenly at the box office, there was no incentive to abandon that low-cost model.
It's only now, with a new executive regime at Paramount, that they're trying to reinvent ST as a tentpole movie property for the studio and willing to invest megabucks to turn it into a blockbuster. (Note that ST '09 has a bigger budget than all six TOS movies combined, or than the first three TNG movies combined -- although that's in raw numbers, not correcting for inflation.)
It's only now, with a new executive regime at Paramount, that they're trying to reinvent ST as a tentpole movie property for the studio and willing to invest megabucks to turn it into a blockbuster. (Note that ST '09 has a bigger budget than all six TOS movies combined, or than the first three TNG movies combined -- although that's in raw numbers, not correcting for inflation.)