JavaScript is dynamic and supports live reload which means iterations are far faster than would be in a compiled language--even for LLMs.
This is especially useful when you're trying to evaluate behaviors while changing state surgically.
There are several compiled languages with live reloading, including C++.
There's no surgery when you're a company with a trillion dollar hammer and every problem looks like a big ass nail.
If you are relying on live updates to change state in a dynamic language then you are not doing it "surgically", unless there is some other definition that means hitting it softly with a large rock.