1)Apple was never a dominant incumbent in mobile. It focused narrowly on the high end market. For the vast majority of the population, especially in emerging markets like Asia and Africa where Andrioid is now the strongest, iPhone was simply unaffordable. Google didn't fight Apple head on but instead take advantage of its weakness in the mass market and open sourced Android which resulted in a flood of low cost smartphones that quickly capture a large majority of the market, the part of the market where Apple never had much of a presence to begin with.

In short, Google played a different game.

2) Nokia rose to power on simple cellphones. It was never a dominant player in smartphones. In fact smartphone was a wide open market with no dominant players when Apple entered that market. So Apple never needed to fight any incumbent.

3) Google still sells 10X more ads than facebook, so it's rather premature to say facebook has beaten google in ads. And even if that does happen eventually, it'd be because facebook avoided fighting google in search ads (unlike Microsoft tried to with Bing) but instead invented the new market of social ads & newsfeed ads. Once again it's the strategy of avoiding fighting the dominant incumbent in its own game and inventing a new game instead.

What exactly do you mean by google > apple in mobile?

After Apple hit the marked everyone was buying an iPhone. Now most of the people have Android phones.

Not really. While the iPhone has been influential and a huge success for Apple, it didn't really kill any of existing smartphone incumbents. "Everyone" was only buying an iPhone for fairly limited values of "everyone" (e.g. excluding several continents). Instead, Android killed off those incumbents, taking advantage of the opening the iPhone had created.

So it's really Google > Nokia (Symbian), Microsoft (Windows Mobile), Palm and RIM, with Apple off to the side somewhere. And the complex, multi-faceted Apple vs Google battle in mobile isn't an upstart vs an incumbent, it is a battle of two upstarts who have become the incumbents.