I personally believe that one good reason for Ruby on Rails becoming so popular for web applications was Microsoft stance of taking too damn long before making .NET an open (and cross platform) technology.
.NET Core has been production ready for like, what? 2 years? A bit more or a bit less, maybe. Both GitHub and Gitlab are older than that. EF Core is not even at feature parity with EF to this day (good thing EF 6.3 supports Core now, but you know, older design, not really great as it doesn’t take full advantage of Core).
I think many of the RoR projects have gone that route because, in the absense of a fully open Microsoft .NET stack, RoR was the next best thing.
Now it isn’t.