Their motivation was partly a 10x speedup. It’s a bit early to tell what this means for Hugo. ESBuild (what Hugo uses to build JS) has great support for TypeScript, but has no type checking (you currently have to run tsc outside of Hugo to do that). Still early, but I suspect this is good news for JS/TS in Hugo.
Also of course interesting to see Microsoft pick Go (a Google “product”) over their own C#.