ES Modules are the glue that binds the whole JS ecosystem together. Whilst ESM is the standard, today a lot of people are using ESM only as an authoring format that later gets converted to CommonJS before being published or executed. Many of today's tools rely on this, meaning the ecosystem is partially tied to CommonJS. Migration is happening but it's slow and non-trivial.
In a way, we bypassed the CommonJS era and skipped directly from AMD to ESM. AMD and ESM are pretty much isomorphic and differ only in syntax. You just run a codemod to get from AMD syntax to ESM syntax - semantics are preserved. Whereas the step from CommonJS to ESM does not fully preserve semantics. CommonJS module initializers are always synchronous. ESM can be asynchronous - you can use `await` in the module initializer.
The article covers a few of the things we've done to retain a very standard ES Module system that is ECMAScript compliant. I think it is this pursuit of standards and desire for robust interoperable packages that led to some of the surprising discoveries.