I think you forget that in it's time IE was massively innovative.
It was IE who added XMLHttpRequest and invented AJAX.
It was IE who added XMLHttpRequest and invented AJAX.
Bill Gates wanted their browser to be the best, but also wanted it not good enough to replace desktop apps. However the right hand didn't know what the left hand was doing. The Outlook team was told to make a web version. They got the IE team to add XMLHttpRequest for their use, everyone implemented what they needed to, then went home and forgot about it.
Then Google recognized what the feature allowed, and used it in gmail and maps. The rest of the internet said, "Wait, what, you can DO that?" Studied it, popularized the technique as AJAX and the rest is history.
It's possible that Microsoft's style guide at the time set three characters as the limit.
Furthermore I remember gmail's keyboard shortcuts being a shock to a lot of people. Me included.
...in 1999. Then IE6 was released in 2001, and then Microsoft scrapped the Internet Explorer team and didn't release another browser for 5 years, leaving us with 90%+ of users stuck on IE6 bugs and non-standard features.
That's what the GP is talking about.