I think it was that and the ui. It looked much cleaner and better than any other web browser, you could even customize it with themes and so on to match your personal taste. I guess people saw the ads and decided to try out their favorite search engines new product.

I want to say that developers and smaller Saas companies might have played a role in this. Smaller businesses are not as big on ensuring everything works across browsers. Most developers use Chrome, so the likelihood of an issue popping up in Chrome is less than other browsers. When an issue does come up with someone using IE and the customer just wants it to work, the easiest solution is to just get them to download Chrome. Many of these customers don't really care what browser they're using and will gladly listen to whatever instructions customer support tells them.

At some point Firefox started being unstable and sluggish to my recollection. At this point Chrome was up and coming but it was pretty fast and clean. So we tried it and switched over. Now there is lots of inertia to switch back. Also if you use a lot of Google services, you can count on them been well tested with Chrome.