My guess is, GP is referring to the significant amount of funding that Mozilla gets from Google. Not sure if it's still the case, but I believe at least for a time, it was actually their main source of funding and basically what kept the whole organisation alive.

So by "don't bite the hand that feeds you" logic, they couldn't be interested in being too adverse with Google, because in the end, this could threaten their whole existence.

Not sure if this is still the case though, or if they managed to diversify.