[zamadatix]

It's not targeting the general purpose OS market it's purpose built for specific kinds of customer use cases. Once you get past that it makes a lot of sense. Well not as in "it makes a lot of sense for you personally to go out and by" but it makes a lot of sense why it exists and sells so much.

[pjmlp]

That is the thing, it doesn't sell at all outside US School system, as the article points out.

[zamadatix]

Decently popular at SMB as well.

The point is it doesn't need to outsell Windows it just needs to have markets it targets and updates for those markets. That it doesn't have updates for markets it doesn't target is irrelevant unless they've maxed out all the markets they target (they haven't yet).