The first (and by far best) game has gone from the iStore as well. Looks like every publisher/company etc. Is desperately trying to get content for their own store/streaming service. It was the same back in the 90s and all it led to was a massive rise in piracy. Still the greedy bar stewards never learn do they.

I think it's reasonable to sustain a few "piracy costs" from pc gamers who can't find an old game anymore, compared to attracting millions of casual smartphone players with a now exclusive title based on a popular series, who are ready to subscribe monthly.
Creating a limited avaibility they are raising the value of the game - Steam is still doing it with Valve games.

I still have the first game installed on my Android phone, but is it the same on GooglePlay and AppStore (as in GOG and Steam) that it will not disappear from your account even if the game is pulled from the store?

Meaning, is it safe for me to uninstall the game and maybe later install on some other (Android) device?

And, is there second game in the series then, on which platforms? I have the third game on GOG, and I just bought the Dark Crystal game too because it will likely be gone as well...

Fine, but don’t try to excuse drm and online streaming as a necessity to avoid piracy, as all it does is create and encourage it.
There wasn’t a second game, stranger things the game (mobile only) was based on series one. Stranger things 3 was based on series 3, hence the 3. I have it installed on iPad and fired it up and it works, wouldn’t risk deleting it as you likely won’t be able to redownload.

The game has now been removed from the console stores as well, leaving it exclusive to Netflix. The chances that the Dark Crystal will share a similar fate have now gone up.

It's funny how the appeal of the online stores was supposed to be convenience.
With this increasing fragmentation and draw towards endless different logins and passwords, the appeal now seems to be the opposite of convenience.

Say it with me, The Cheat:
Licenced videogames will never last forever!

Not entirely sure, but some apps I used from the Play Store were no longer downloadable after they were removed (not sure if they were banned or simply delisted by the publisher's request). Worst case scenario, if possible, create an offiline back up of the game (although Google's DRM might be an issue in this case).

On iOS, re-installing delisted games used to be possible, but the last time I used an Apple device was ten years ago, so it might have changed. As I recall, you had to do it through iTunes, which I believe doesn't even support managing your apps anymore.

For Android, it's not possible, not even for apps you paid for, which I know because that happened to be with an alarm clock app I once bought on Google Play. The developer when out of business, the app was delisted, and I never could get the app back after having uninstalled it. It still shows in my purchase and install history, but there is no way to install it.

The good thing about Android is that it officially supports side-loading, and there are some trustworthy APK archives out there that keep old versions of APKs that used to be available from Google Play. In a lot of cases, you can find the file there and re-install the app. Unfortunately, they of course don't archive paid apps. And the archives might be much more empty for recent stuff due to the switch from APKs to AABs on the Play Store.

The best way is to back up the apps you still have installed. This is pretty easy through enabling USB debugging and using adb (get list of installed packages, get path of specific package, copy .apk to computer). This way you can re-install it from your local copy later, unless the app has some other form of online DRM in it (I don't think Google adds anything, I never had any issue restoring apps from local backups).