It's like Google Code. Google didn't particularly want to be in that business, but Sourceforge was complete shit, and the open source ecosystem was key to their business. So they competed, seriously improved on the status quo, and when something better came along (github), they backed away, job done.
So leading this market doesn't matter to google. If they got completely outcompeted, I'd say they'd be delighted.
The cynical take on this is that Google just wanted to increase lock-in to its own browser; however, I think it's more a case that Chrome is a runtime environment for Google products as much as it is a web browser.
The actual reason is they have to pay browser vendors like Firefox hundreds of millions of dollars for having Google search as their default search plugin. Plus, they are at the mercy of other companies if they decide to change the default search plugin. All this plus the mobile game, if you have a browser and that has a major market share you can be rest assured to send the traffic to your sites.
Same with android, as long as you have your stuff(OS, Browser) installed on other people devices, getting traffic from their is easier. Which is why they give it away for free. Have a big market share and you win by default.
Other projects in this space include Android One and Loon.
Power corrupts...
Auto industry? I'm assuming you mean self driving cars, which, at this point, are still in the concept phase. Space industry? Did I miss something, is Google launching rockets?
There are many other companies that are way more diversified than Google.
http://en.wikipedia.org/wiki/General_Electric
http://en.wikipedia.org/wiki/Siemens
http://en.wikipedia.org/wiki/Yamaha_Corporation
Plus, expanding into a wireless carrier makes way more sense for Google than any of their other ventures. One of the limiting factors of internet use in the first-world is terrible carriers with data caps.
Multiple generations of prototypes and hundreds of thousands of miles driven is well past the concept phase.
[0]-http://en.wikipedia.org/wiki/Planetary_Resources
[1]-http://www.miningweekly.com/article/planetary-resources-laun...
"Google, which has its logo on the side of the rocket, has exclusive online mapping use of its data."
The really funny bit is that near the end of Steve Jobs's life (per the biography), Larry Page asked him for advice and of course he said "focus on doing a few things really well, cut out everything else."
Seems Larry decided he knew better.
Browser, email, self-driving cars. Lots of other stuff too...
Leading in memory usage perhaps
not a sub, but there was/is? this http://sanfrancisco.cbslocal.com/2014/01/07/google-launches-...
Apparently he did. In the same biography, Isaacson wrote that "asking for advice to run a company" was just a clever way for Larry to visit Jobs in peace, playing to his ego, so to speak, as Jobs still held a grudge against Android.
Google is a very different company from Apple anyway. At Apple, innovation runs top-down, from the likes of Jobs and Ive to Foxconn workers. At Google, innovation runs bottom-up.
Not that I'm convinced it's always for the best. Throw all that control into somebody's hands and even if they think they're doing what's best, they might make mistakes with far-reaching consequences.
Despite its impact on our lives it's important to remember that tech makes up just one segment of our massive economy. I have yet to see Google get into Aluminum smelting, residential construction or toothbrush manufacturing.
[1] http://googleblog.blogspot.com/2014/01/introducing-our-smart...
[2] http://www.wsj.com/articles/google-to-collect-data-to-define...
Having a goose who lays golden eggs (search + adsense) to subsidize development?
They don't dominate every industry but they have to diversify in industries to keep their shareholders happy which in turn is good for everyone.