I'm not sure where your information comes from because it sounds very suspect to me. Sure XHTML was a thing in nerdy circles, I know because I was one of them,

I'm not sure where your information comes from because it sounds very suspect to me. Sure XHTML was a thing in nerdy circles, I know because I was one of them, but we were hardly the majority. The vast majority of sites were "HTML 4.01" others were at best "XHTML 1.0 Transitional" (which in practice meant the same thing). Those using pure XHTML were relatively few. And of those who did, no major site served it as such because it would have locked out IE users, IIRC.