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.

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.

Markdown has been extremely popular since far before GitHub existed.

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.

Sure, but it became kind of the default with GitHub taking a lead position in code repository services.

Imho the real strength of markdown is it forces people to stick to classes instead of styling. "I want to write in red comic Sans" " I don't care, you can't".

And markdown tables are harder to write than HTML tables. However, they are generally easier to read. Unless multi line cell.

I usually just write html tables, then convert to markdown via pandoc. It's a crazy world we live in.

Is it really that much easier to write `<br>` and know that it isn't a problem, than just write `<br />`?

It’s much easier to have to remember fewer rules and for things to be ok if you get some wrong, yes.

Especially for casual users of HTML.

Bad reasoning.

“Always close your tags” is a simpler rule (and fewer rules, depending how you count) than “Close your tags, except possibly in situations A, B, C…”.

I've been closing my tags for 30 years and I assume that I will for the rest of my days. I like that it validates as XML. Historically I used XSLT a LOT.

It triggers the linters so often. I shall keep my <input> tag open.

<script /> is invalid HTML, and <img></img> is also invalid HTML. There's no way to avoid knowing HTML syntax.

But learning about self closing tags is an additional rule

User input data is always to be treated as suspect when it reaches the server and needs to be scanned and sanitised (if necessary) before accepting it for processing. Markdown makes this a lot easier to do and this is why it became popular.