They did make a good browser. However, their market share is not down to better browser or "some advertising." They use their other assets (search, youtube, android, docs..) to make chrome the "default" option.
It's a dominance breeds dominance cycle... a hallmark of modern monopoly.
Chrome wouldn't have gotten anywhere if it wasn't a very good browser. It is good. But, I don't think it could have been that kind of wipeout without leveraging google's greater web dominance.
There was a time when IE was a good browser and the default one. They dominated. A few years later, Mozilla had the better browser. Firefox slowly climbed to the middle, by being very good. They never got to 50% of the market.
IMO, during the IE6_v_FF days the feature and quality gap between browsers was at its highest. Much bigger than Chrome_v_FF ever was. Still Chrome today is far more dominant than FF or anything ever was... except IE in its monopoly day.