Comment by jillesvangurp

Markdown got there first/early depending on your perspective. Things like AsciiDoc got popular much later when AsciiDoctor was released around 2009 (though it technically existed already when Markdown was created) and is aimed at people who care about structured documentation. It's not aimed at casual users.

Likewise, things like org mode, which also emerged around the same time, catered to a niche of emacs using people. Which almost by definition is a subset of techies. It wasn't a logical choice for a mainstream blogging tool.

Markdown was aimed at people that used blogging tools (initially), and later any other kind of tool that accepted text. It spreading to tools like Slack, Github, etc. is no accident. Github actually has supported plenty of alternatives for documents. But they picked markdown for issue tracking, pull requests, etc. Because they had to just pick something and Markdown was the most popular.

By the time AsciiDoc became more popular (2009ish), Github was already being developed. With Markdown support. AsciiDoc was a niche thing, Markdown was already somewhat widely used then. It was an obvious choice. Them picking Markdown was important because the whole OSS community started using Github and got exposed to Markdown that way.

The rest is history. Other formats existed (textile, and various other wiki formats). They have features that are important to some people. But getting people to switch who don't really care about those features is hard. It's a bit like VHS over Betamax. Was it better. Not really. But it was there and video rental shops had to pick a format. And that wasn't Betamax when the dust settled.