I've been at more than one company that migrated _from_ MediaWiki to Confluence. It usually boils down to "non-developers have to use this and Markdown+plugins is hard".
Turns out no matter how much better the thing is, the users have to know what they're doing more than the operators do.
visualeditor has been a thing for a long time now, no non technical user needs to ever touch markdown
https://www.mediawiki.org/wiki/VisualEditor
It's the same GUI WYSIWYG interface you get by default if editing a page on public wikipedia.
I'm not surprised. We're trying to migrate from Jira and Confluence (because we can't have our data outside our servers), and while Jira has many alternatives, it's difficult to find worthy competitors to Confluence. They either have an awful UI/UX, or don't have as many features. We're looking at Xwiki, but simply try to have multiple users simultaneously edit a table and you'll see why everyone prefers Confluence...