FTR Trove hasn’t been taken down, however games have mostly been removed, presumably as their lease came to an expiry, but also a few Originals may be gone.
The only additions have been the individual DRM-Free Extras from each month so, naturally, the net effect is that Trove has been slowly shrinking, rather than growing or even staying the same.
The concept of Trove, when it launched, was to provide a library of yours-to-keep, DRM-Free games for anybody with an active subscription, however a shrinking library is not exactly a great selling point.
It seems realistic that Humble was paying some kind of fee, maybe a one-time payment, to developers or publishers, to feature their games in Trove.
With the rise of true subscription services, run by tech giants with deep pockets, it stands to reason that games have been lured away from Trove, since Humble can’t offer as much money, visibility, etc.
Of course, sub services are run on what is supposedly an insurance-model, where a lot of inactive players subsidize a minority who actually can consume the content.
My suspicion is that since we’re still in the inception phase, these services may not be running at a profit, but instead are being subsidized by the profits these companies make elsewhere.
In this scenario, smaller players that cannot find a niche, will likely wither and/or die, but at some point service owners will want to the competition phase to end and bring their acts in the black.