Machine code yes (along with Spidermonkey, JSC and Nashorn), the timeframe around 2005-2010 saw the introduction of JIT'ed JS runtimes. Back then however JS was firmly single-threaded, it was only with the introduction of SharedArrayBuffer that JS really started to receive multithreading features (outside of SharedArrayBuffer and other shareable/sendable types, a runtime could opt to run stuff like WebWorkers/WebAudioWorkers in separate processes).

Early Node f.ex. had a multi-process setup built in, Node initially was about pushing the async-IO model together with a fast JS runtime.

Why Bun (and partially Deno) exists is because TypeScript helps so damn much once projects gets a tad larger, but usage with Node hot-reloading was kinda slow, multiple seconds from saving a file until your application reloads. Even mainline node nowadays has direct .ts file loading and type erasing to quicken the workflow.