Google seems much too sure of itself making this change. I hope their arrogance pays off just the same as Microsoft's did with IE.
Nothing stops us from doing the same thing again. I've been recommending Firefox to all my family/friends/colleagues for years (ever since I've seen the writing on the wall for Chrome). While Firefox isn't perfect, it's in a much better place than Chrome is, and meets the the needs of nearly 100% of people.
No, it was driven by having a banner in the most privileged spot of the Internet, Google.com (the most visited site in the world with 0 ads on the homepage) saying that was faster and more secure than the alternatives. In fact Firefox benefited from some free ads on Google.com against Internet Explorer before Google developed Chromium.
Later Google's ability to buy installs and put it on google.com came into play, but for at least the first 5 years and probably longer, chrome was a far faster, more secure, and more reliable choice. They also pioneered the multi-process model to isolate different components of the browser.