At the time IE 6 was released, it was the best browser available. The problem was Microsoft acted is they had “won” and stopped updating it for years, where it calcified and became the hot mess we all knew and disliked.
Yes, it was better but it didn’t really count, as Apple just emerged from its near-death experience and Steve Jobs cut the deal with MSFT to make IE 5 the default browser for the Mac.
Apple’s marketshare was tiny back then and many people in the industry didn’t think Apple would be relevant much longer.
Ironically, after the 5-year deal had expired, Apple shipped Safari 1.0, which was better than the vaunted IE 5 for Mac.
Apparently they got close enough to getting this working that a bunch of South Korean banks and such bought into it heavily, which meant you could only do online banking in that country, for a while, on either a windows phone or an actual windows machine.
However, they narrowly missed getting developer buy-in on that stateside, before the whole "XMLHttpRequest" thing went crazy, and we started building javascript apps for everything.
Besides, nobody got promoted at Microsoft for staying the course and making incremental improvements. Once there were no more balls to be knocked out of the park, developers moved elsewhere to buff up reviews and get bullet points for major projects.