Where in the world did you get these ideas?
> They desperately need new revenue streams to support their primary product (the Firefox browser)
No, they don't. The Corporation receives almost half a billion USD annually—over 2.5x what they were bringing in 10 years ago (when they were supporting 20+% of the world's Web browsing; for comparison, they're now at <5%). And whatever they make from MDN Plus, it likely won't even be half of what they flush down the toilet on the marketing department every year.
> since it's non- revenue earning
What? There's a reason why Firefox is Mozilla Corp's primary focus, you know—because it's one of the few things that does pay for itself (and then some—most of Mozilla's adventures are funded by revenue tied to Firefox).