The evolution is fairly simple: python is very easy to setup, especially with django for working on the web, and for writing scripts quickly it work really well

The evolution is fairly simple: python is very easy to setup, especially with django for working on the web, and for writing scripts quickly it work really well when everything is just an 'import' away. Then as the product gets bigger, you'll hire python developers to keep up with the workload - and the best ones will be the ones who have committed their lives to Python. So you'll now end up with more and more python code. Before you know it, you aren't writing small scripts anymore, but now you are writing quite large features, that take weeks and that require intimate knowledge of the code base so you don't keep backtracking and repeating yourself. But Python doesn't help you at this point, you traded static types for flexibility and now you have to pay the price. At this point you're screwed, too many man hours spent on the codebase to redo it, so what to do? Well if you have the man power, build your own static type checker of course! I mean after all, if you have 100s of engineers who cares? You just throw more people at the problem until it goes away. Then wrap it up in a nice little package, and slap yourself on the back while you ride the instagram bubble.