Chrome was widely adopted because it didn't suck and because google--a brand they already learned to trust for search--was constantly beating them over the head to upgrade.
IE wasn't just bad on technical grounds. It genuinely sucked for everyone. It was constantly getting infected with toolbars, popups, and generally crashing all to hell. It was confusing for people to use even when it wasn't any of those things.
Chrome was adopted by the majority of users because it worked at all. IE just didn't.