It seems like ages ago that Microsoft's Internet Explorer was the undisputed king of the browsers. In fact, between 1995 and 2012, it stayed above 50% market share, and in the early 2000s passed 90% for a while. Now, less than 15% of all browsing is done with Internet Explorer.
Its downfall started well before 2012, though. In the early 2000s, Microsoft got increasingly lazy and there were no real performance or security improvements to IE for years at a time. The Internet was changing rapidly, but Microsoft wasn't changing with it. That paved the way for much better alternatives like Mozilla's Firefox in 2002 and Google's Chrome in 2008.
Even with the renewed competition, it took Microsoft a long time to get its act together. In fact, it didn't create a really competitive browser until Internet Explorer 9 in 2011. Even then, it was still trailing other browsers in speed and security.
Fortunately, Microsoft kept working and its latest browser, IE 11, is actually a pretty good, reasonably safe browser to use if you don't want to switch to a third-party option. Unfortunately, the damage is done.
No matter how good Microsoft makes IE, it will always have baggage. I'm not only talking about the 20 years of old code Microsoft needs to keep in place for "compatibility."
Just the name "Internet Explorer" is enough to turn off a lot of modern computer users. That's why after 20 years, Microsoft is taking a radical step and making a new browser for Windows 10 with a new name.