It's not dominant, it's apparently perceived that way within tech circles because they focus on tech.

There's not a good apples to apples comparison of public data, but for instance...

Medium 20k authors per week: http://recode.net/2015/09/28/ev-williams-medium-raises-57-mi...

WordPress.com average 12.7m posts per week: https://en.blog.wordpress.com/2016/01/06/the-2015-wordpress-...

They remained 'elitist' for just the right amount of time, making people grave for the privilege to sign up. Svtble pulled the same stunt.

But medium timed things right and opened up to masses sooner. People signed up in droves. 'svtble' stayed elitist for many more months, but were medium forced their hands, but it was already too late.

Read what 37Signals/Basecamp who has spent 15 years building their (huge) audience on their own site says:

https://m.signalvnoise.com/signal-v-noise-moves-to-medium-c8...

I think the number 1 reason is reach.

Reach is exactly right. Also good for audience building.

That said, I agree with most of the complaints about Medium as well.

I've been wondering this, too, and design/ease-of-use aside, the biggest argument I've heard (and observed) is the network effect. Even trivial Medium posts get at least a handful of favorites and 1-2 comments. A built-in audience is likely an easy sell for the majority of folks.

I guess that makes sense, but there are certainly other platforms with an "audience", like Tumblr, etc?

Medium started out with Twitter sign in, which means their early users were all Twitter "influencers". The way I look at it, it's a blogging wrapper layer built around Twitter social graph. When you sign in with your Twitter account you automatically follow everyone you follow on Twitter on Medium.