It's pretty funny, because Firefox was like the best browser of the late 2000s, until sometime around 2011 they became adware for a decade just to make a comeback as a privacy focused browser again. So it's not like this hasn't happened before. I always wondered peoples newfound enthusiasm TBH.
Edit: I swear this happened when they switched to the rapid release cycles and FF went from version 6 to 20 in a few months and at one point it became super slow and came with unwanted ad extensions. It's almost like the internet was scrubbed of this. https://en.wikipedia.org/wiki/Firefox_version_history#Rapid_releases