It's easier to gradually refactor a legacy program to a different language using the Strangler pattern when they run on the same runtime and there's easy and performant interoperation between old and new code. I wouldn't call it stupid.
yeah but in most cases it's better to just rewrite everything fresh. it's more of quick fix to me.
Rewriting everything fresh is not always an option in terms of cost and opportunity.
We are actively in the process of rewriting a legacy system using the Strangler pattern, 50 devs and 2 years later it's still less than 50% because business wants new features as well, they can't afford waiting 1-2 years with no business value added in the meantime.
Why is just running say your Ruby existing program on Truffle with a big performance gain stupid?
A lot of the languages use C extensions and running them on the JVM is faster then using the FFI to call them from the JVM.