Also, if you look at browser stats even today, arguably IE has an "unfair" share of the market -- but such things are hard to be certain of ("What is a 'fair' market share for the now much, much improved IE browser?").

The biggest thing MS did was probably to give away the browser for free, subsidizing the development of the browser, with profits from windows licences. That dumping effort effectively killed the market for (paid for) browsers -- eventually even Opera gave up charging end users for its browser.