It's surprisingly hard to find an answer to this (an FAQ on the Bun site would be a good idea?), but I suspect it has to do with reimplementing some stuff (bund

It's surprisingly hard to find an answer to this (an FAQ on the Bun site would be a good idea?), but I suspect it has to do with reimplementing some stuff (bundler, package manager, test runner etc.) in a compiled language (Zig) rather than using the JS runtime for everything (this is probably also the reason why Bun integrates so many functions into one "kitchen-sink" executable), and using a JS runtime which is faster than V8 at least in some regards.