People also forget that Microsoft decided to tightly couple their browser to their operating system, not for any technical reason but so that they could fight the antitrust charges levelled by the U.S. DOJ due to their bundling practices and misuse of market power.

Consequently, I'm of the opinion that they made a rod for their own back and it became very costly to maintain and enhance their browser. Truly, they were hoist on their own petar!