If you want to advertise, have a newsletter that people can opt into.
If you need money, allow people to pay for just Firefox.
Everyone gets angry and has an opinion of how this sucks. There's no way for this to work out for Mozilla. Nothing they do will work or make everyone happy.
Google won.
Because Mozilla and its execs were asleep at the wheel while Google started to eat its share. This is what you get when you stop competing.
I mean... it was probably that too, but Google abusing its search monopoly to market Chrome probably played a major role as well. Or if you like - Mozilla's mistakes are such that Google probably could have won fair, but that's not what actually happened.