Indeed Nesoid, Snedoid und Gameboid are removed.
Compared to Apple, Google is very slacky by the inclusion of programs in their own App Store. There are no past examination.
This does not mean Google hasn't any rules. As you can see there is a report on "Android Police".
So now all channels of the developer Yong Zhang were removed from the market, deleted the associated account. Zhang had focused on the emulators and here among other Nesoid, SNesoid GameBoid and various apps offering.
The question of why Google has now decided to distance, one can only speculate, because the company does not comment on individual cases.
The community also suspected in a row as quickly the pressure of the games industry, which in recent years, again and again - has taken action against emulators - but with very changeable success. After all, before not too long ago with the emulator PSX4Droid also another developer was thrown out of the market.
However, there is also another possible explanation: On Reddit there is a discussion, that Zhang might violate the license of the free software licence GPL.
After all his emulators are based quite clearly on free software, but Zhang didn't make his code public and also didn't make it clear where he got it.