I tend to attribute it a lot more to Chrome's many years of deceitful marketing and bundling itself as adware in other products including Adobe products.
Depending on your view of Firefox OS and if it was "Firefox enough", the "Mozilla Foundation doesn't focus enough on Firefox" is a relatively new complaint, but Firefox's biggest losses in market share happened well before even the Firefox OS effort.
(And the Firefox OS effort was to try to keep a competitor against Android and its Chrome hegemony viable, so it was a direct reaction to lost market share. And the current complaints of "Mozilla isn't doing enough Firefox" today are all the complaints about the various ways that Mozilla is trying to diversify their revenue stream and that too seems obviously because of lost market share, not the cause of it.)