Cheap and plentiful dev talent. Grab any random guy (and at these shops it's always guys) off the street and bang you've got a python dev.

There's always going to be an agility multiplier so long as VC is flowing and getting an mvp and a high head count is worth more than any kind of sustainable product.

>I struggle to think of any benefits of dynamic typing on a reasonably sized code-base

Being able to define and initialize types at runtime offers more flexibility and it's quicker to develop in.

I'm frankly surprised nobody brings it up more often but the prototypical example of "static typing done right" - Haskell - is talked about nearly constantly but when I look for actual software I might use that's written using it.... there's so little it's almost embarrassing. One obscure window manager, one obscure VCS, facebook's spam filter and some tool for converting markup.

Given a sprinkling of asserts, a decent linter and a high level of test coverage I don't see much of a benefit to adding static typing.

> I struggle to think of any benefits of dynamic typing on a reasonably sized code-base (e.g. 50k+ LOC).

And yet, it's done all the time with great results.