It’s losing them some high-level writers, but there are so many writers to step into their shoes, they aren’t losing money. They earn money from subscribers (before they payout the writers, Medium first gets a set percentage of the total subscriber payments) plus all of the content is available to Medium to use, display, sell, etc in any way they want to. That’s a big money pot.

The tweaks are intended to encourage more content, less payout.