Python, Ruby, JavaScript

Python ended up ‘specializing’ in data contexts, thanks to Numpy / Pandas, and as a result, ended up becoming the first exposure to programming than anyone doing data stuff had. That was millions of people. In that space, it had no competitors.

Ruby ended up ‘specializing’ in web dev, because of Rails. But when Node and React came out, Ruby on Rails had to compete with Nodejs + React / MERN as a way of building a web app. Since people first learning programming to build a web app would usually start with javascript anyway (since a lot of very first projects might not even need a backend), it was a lot easier for the Nodejs/React route to become the default path. Whereas if you were a data scientist, you started on python, and as you got better, you basically just kept using python.