Mozilla decided that providing this feature serves their users better than not providing it. Especially that users can turn it off. ( https://mat.tl/disable-eme-in-chrome-and-firefox.html )

Firefox was forced by Chrome, and Chrome in turn was probably forced by trying to remain a viable platform instead of Netflix et al. simply providing their own desktop apps. (Though I'm only guessing, if you have direct knowledge of the what and why, please do share.)

> Firefox was forced by Chrome, and Chrome in turn was probably forced by trying to remain a viable platform instead of Netflix et al. simply providing their own desktop apps.

The kind of users who are not opposed against DRM already have lots of browsers to choose between. On the other hand, people who are will now feel deeply betrayed by the Mozilla Foundation.

And then there are people like me, who are opposed to DRM, yet don't feel betrayed.

If you're opposed to a browser that can be used by DRM modules, Firefox was already not an option, since it supported NPAPI, and therefore DRM as Flash, Silverlight, etc. If you were using Firefox, you were already accepting that compromise. EME is simply a continuation of the status quo.

> will now feel deeply betrayed by the Mozilla Foundation.

Was there an explicit or implicit covenant by Mozilla and those users?

> Was there an explicit or implicit covenant by Mozilla and those users?

I believe Mozilla's clear stance on DRM in the past (and its clear differentiation against other browser vendors in this respect) is near to such an implicit covenant.

Why would the producers of the content choose to license it to DRM-free delivery services though? Unless you are suggesting that Desktop Linux users are a viable market segment for triple-A content producers themselves, which I doubt.

I don't know the answer to that, but it's a market that startups could potentially capitalise on. It would also not just be desktop linux users, but anyone not using the top N web clients (where N is chosen by said media provider to provide the best cost/benefit to maintaining the DRM on those platforms).