Making Firefox even less desirable by "googlifying" it pushes Firefox users away and kills its image of a viable competitor. That's exactly what Google is paying for.
Why would Google destroy the cover they have for keeping control over Chrome and 70% of internet users, just to squeeze a bit more ad revenue from what, 2% of users?
Firefox has around 2% share, it hasn't been a viable competitor for a long time.
Copying Chrome at the expense of loosing even more of their user share has been Firefox's MO for the last decade. It doesn't have to make sense to be reality.