MS had a motto back in the day "embrace, extend, destroy" which was said to sum up their approach to standards and technologies they didn't control.
First MS would adopt the standard (embrace), then they'd start adding to it in ways which were useful but not available outside the MS products using the standard. Because they were so big their reach meant that these extensions would often become widely adopted and once this happened you effectively had to be running the appropriate MS software to have whatever it was work properly.
At which point the standard / technology ceased to be any threat to MS as while they may not control the paper standard, they controlled the vast majority of how it was being used in the real world.
The fear was that with IE being the defacto standard browser for 90% of machines, MS could have potentially take control of HTML and the other web standards and damaged or destroyed the open web.
First MS would adopt the standard (embrace), then they'd start adding to it in ways which were useful but not available outside the MS products using the standard. Because they were so big their reach meant that these extensions would often become widely adopted and once this happened you effectively had to be running the appropriate MS software to have whatever it was work properly.
At which point the standard / technology ceased to be any threat to MS as while they may not control the paper standard, they controlled the vast majority of how it was being used in the real world.
The fear was that with IE being the defacto standard browser for 90% of machines, MS could have potentially take control of HTML and the other web standards and damaged or destroyed the open web.