[jupp0r]

> What caused the drop in popularity in RoR?

Async/await. JavaScript and all other modern languages and frameworks have a great concurrency story. Rails still hasn't (but it's coming next year, it's been coming next year for a decade).

[speleding]

The concurrency story in Ruby is fine. We've been using multi-process Ruby scripts in production for over a decade. The pre 2.7 ruby had some issues, but it's been solid for years. The async/await programming paradigm is painful by comparison. Sure, there are languages out there that have been designed from the ground up with concurrency in mind, that have an even better concurrency story, but those do not put developer happiness(™) front and center.