I suspect it’s the latter. I would guess V8 with a thin wrapper and a ton of effort from someone who cares about perf to port all the native goodies of node would get similar wins.
Absolutely. And it has been done already, JustJS[1] has made it to the top 10 fastest in the TechEmpower benchmarks. It’s Linux only though, and not nearly as complete or easy to use, which makes it unappealing for real world projects.
[1] https://github.com/just-js/just