Web development has gotten much more complex these days and while RoR still strong, Python has gone "mainstream"

https://www.guru99.com/images/1/021020_0523_PythonvsRub1.png

This chart alone should be telling. Ruby has more learning curve, smaller set of libraries and stable but slow rate of innovation. The returns aren't that great for something like Python developers who can be trained on most tool in its ecosystem.