I think that the practically available type checkers evolved to a point where many of the common idioms can be expressed with little effort.

If one thinks back to some of the early statically typed languages, you'd have a huge rift: You either have this entirely weird world of Caml and Haskell (which can express most of what python type hints have, and could since many years), and something like C, in which types are merely some compiler hints tbh. Early Java may have been a slight improvement, but eh.

Now, especially with decent union types, you can express a lot of idioms of dynamic code easily. So it's a fairly painless way to get type completion in an editor, so one does that.