That number should grow again. It's becoming increasingly obvious what a privacy leak Chrome is, and Firefox is just as good, making it an obvious choice for anyone who cares about privacy.
Mozilla (Firefox) management thought that installing a Mr Robot advert extension on people's computers, without asking, was a good move, and defended it until the internet outcry got loud enough. With management like that, I find it hard to trust them. Default-installing Pocket was also not entirely defensible and was probably money-driven.
Essentially, both companies have done anti-privacy and untrustworthy actions, and choosing the lesser evil is hardly ideal.
The difference between Mozilla and Google is substantial. Whenever Mozilla gets this wrong it is usually a goof of sorts, when Google gets it wrong it tends to be policy. See 'AMP'.