Comment by nathankleyn 9 hours ago
Personally I think Markdown got _really_ popular not because it is easier to write but because it is easier to read.
It’s kind of a huge deal that I can give a Markdown file of plain text content to somebody non-technical and they aren’t overwhelmed by it in raw form.
HTML fails that same test.
I'm sure Markdown was already popular, but I agree with the OP that GitHub made it orders of magnitude more popular.
Previously its popularity was somewhat similar to RST.
People had already ditched writing HTML for years before Markdown came out.
People were just using other markup languages like rST.
Other attempts had already proven HTML to be a bad language for rough documentation. Someone then just needed to write a spec that was easy to implement and Markdown was that.
Or because it was the default in GitHub with an ad hoc renderer.