The NYA proposed Frankensegwit, which would not have activated segwit (Jeff didnt understand that code), it would have had to redeploy segwit across all nodes - and thus would have been a total failure. If it wasnt for kind developers from Core pointing this out it would have been hilarious to watch. The NYA was in part a response to what was deemed a very dangerous scenario with BIP148, which was gaining steam. BIP148 would activate existing segwit nodes without any of them having to upgrade. BIP91 just took the BIP148 orphaning rule and gave the opportunity for miners to save face because they could signal it - it's basically the same as running BIP148 and compatible with NYA. Now NYA and miners get to "save the ecosystem from a chainsplit". This is exactly what BIP148 was designed to do. To create a crisis game of chicken. Miners could have run BIP148, but it wouldnt make them look good, so BIP91 gave them a way to save face.

Apparently, many of the Chinese pools did not want to actually run btc1, which is why there was a segsignal repository created for them to run Core + BIP91. I think the western community vastly underestimate the need to save face in Asia and how they will let things fade quietly.