As one comment under said, it's a small Norwegian family company (5 employees) that's been around since at least 1998. And they've always focused on what they do.

From open Norwegian business data (https://www.proff.no/selskap/refsnes-data-as/sandnes/it-kons...), it seems like they have a yearly revenue around $4.5M USD. From the annual salary expenses, those five employees either make bank - or they hire a lot of consultants from overseas.

So I guess it's a good example of first-mover advantage.

Most people seem to think w3schools has some form of association with the W3C. It is actually run by a small family company, Refsnes Data AS, from Sandnes, a depressing city on the western coast of Norway.

Perhaps what the world needs is more depressing cities then...

It's how I learned web development 20 something years ago. They have simple, clear, entry level tutorials on HTML, CSS, JS and a number of other languages that give you enough to become somewhat productive on the web, so you can be interested in deeper content. It's an institution.

I downloaded the W3Schools offline dump zip archive, which was under 50mb IIRC, from a friend when I first started learning programming because I didn't have access to proper internet. That helped me a lot to learn to code.