OpenResty consistently handles 5 times more connections than Node.js, without requiring any of the continuation passing nonsense. As usual, popularity doesn't reflect upon quality at all -- Node.js is the Kim Kardashian of web frameworks.
If you're making an entire web application with a lot of front-end code that is already written in Javascript it is an added cost to also support C and Lua.
A lot of important development time can be retained by not having to write the same functionality in multiple languages.
A module can be written in Javascript and used on both the client AND the server.
Don't conflate mainstream media fashion with the sort of pragmatic convergence that has been a big part of driving the adoption of node.
"Raw speed" over everything else is the Yngwie Malmsteen of programming language metrics.
Also you don't need to program entire application in open resty. Just the idea of using lua instead of nginx mini- language for the config files can be a good enough reason to give it a try. Every body uses nginx anyways for their front end, no?
And the best part is it is 100% compatible with nginx config file. So all your default locations and blocks that already work with nginx are going to work with open resty. You can now organize and program it better.