Topps wanted the cash cow that was HeroClix, and got the rest of WK along with it. When they decided HC wasn’t worth their effort any more they shut the whole thing down.
When NECA picked up the remnants later, mostly just for HC, they must not have seen high enough profit margins to bother restarting any of the other lines. They only made a half-hearted attempt with the Pirates license with that “Shuffling the deck” game, which faded into obscurity pretty much before it even began. They used the Mage Knight license to make a really excellent board game (currently ranked #22 on BGG), but it’s “Mage Knight” in name alone and has virtually nothing to do with the old miniatures game. ‘Mechwarrior and Crimson Skies reverted back to whomever they were originally licensed from (Microsoft?) and NECA never got them.
The whole collectible games market in general seems to have quieted down a lot in the past few years too. There are still several big ones still out there going strong, and the occasional new one, but it’s not like the mid-2000s where it seemed like there were five new collectible games being launched every week.
ADDED: Another factor, maybe less obvious, can be seen in some of the backlash directed at mobile and online games, and particularly EA, for their horrendous “loot box” and microtransaction systems that are bleeding consumers for every penny they can get. The whole blind booster system used by Pirates and so very many other collectible games is almost the exact same thing, just with an an actual physical element to it, so it didn’t seem as bad at the time.