No, I think it's because Microsoft failed their way out of the browser game and then we got auto-updating browsers. IE6 did a terrible job of implementing web standards, with MS deciding to just make up their own damn standards. And updates to IE6 were locked to Windows updates, IIRC. IE7 was big step in the right direction, but it wasn't until IE11 that you could be reasonably sure that developing in FF/Chrome meant it would work roughly the same in IE. But even then, MS wouldn't let you go past IE9 on XP, so in a lot of ways IE9's marketshare was tied with XP's, which took years to dwindle away to a point where you could safely ignore it.

Then Chrome rose to power, which is repeating some of MS's failures with "their own damn standards" here and there, but is largely avoiding the big failures because the browsers update themselves now. Shy of people being stuck on X version because of their work situation, you don't have to worry about a huge chunks of your userbase being stuck on a 5 year old browser anymore because most folks are getting auto-updated and those updates aren't arbitrarily locked behind OS versions like IE was.