> HTML absolutely used to “say how things needed to be rendered”: with tags like B, I, FONT and so on. It was developed when documents were expected to be WYSIWYG-style markup (Word/WordPerfect, Latex, etc).

Yes, those tags do exist. However, their story is more complex, and intertwined with the rocky road towards standardization. And their importance gets easily overstated, even though they were a boon for budding website builders dabbling with HTML in the late 1990's. [0]

These didn't exist in the original HTML document as drafted by TBL. They were tacked on in what we know as HTML 2, which wasn't an W3 recommendation but an IETF RFC. [1] They were kept in HTML 3.2 which is the first formal W3 recommendation recognized as a standard in january 1997. [2]

HTML 4.01 deprecated FONT, CENTER, U and STRIKE in december 1999, barely 2 years later. [3] At the same time, HTML 4.01 introduced and promotes the use of stylesheets for presentational purposes to overcome the limitations of HTML. [4]

> Style sheets represent a major breakthrough for Web page designers, expanding their ability to improve the appearance of their pages. In the scientific environments in which the Web was conceived, people are more concerned with the content of their documents than the presentation. As people from wider walks of life discovered the Web, the limitations of HTML became a source of continuing frustration and authors were forced to sidestep HTML's stylistic limitations.

> ... Style sheets solve these problems at the same time they supersede the limited range of presentation mechanisms in HTML.

Moreover, the use of the elements that weren't deprecated - I, B, BIG,... - was discouraged by the HTML 4.01 specification itself in favour of stylesheets. That's since December 1999. [5]

> The following HTML elements specify font information. Although they are not all deprecated, their use is discouraged in favor of style sheets.

Also, I would have to disagree with this:

> CSS was designed to strip that away only after people decided the future of hypertext should look more like XML.

The development on XML happened at the same time as HTML and CSS. XML was first published in February of 1998, well after HTML 3.2 and before HTML 4.01.

However, XHTML 1.0 was based of HTML 4.01 and was basically a transposition of HTML 4.01 using XML. XHTML 1.0 only became a W3 recommendation in January 2000, well after HTML 4.01 and XML were first published. [6]

Moreover, CSS 1 was first published in 1996, CSS 2 in May 1998. The first draft of XHTML only was published in December of 1998, well after CSS was established. [7]

My point is that all of these technologies were developed by committee. In separate Working Groups, which didn't necessarily align their efforts. That's basically why the road towards convergence was - and to a degree still is - this rocky.

And all of that is discounting the browser wars with vendors such as Microsoft applying their own interpretation of the specifications in their engine.

[0] http://www.martinrinehart.com/frontend-engineering/engineers...
[1] https://www.ietf.org/rfc/rfc1866.txt
[2] https://www.w3.org/TR/2018/SPSD-html32-20180315/#body
[3] https://www.w3.org/TR/html4/appendix/changes.html#h-A.3.1.2
[4] https://www.w3.org/TR/html4/present/styles.html
[5] https://www.w3.org/TR/html4/present/graphics.html#h-15.2
[6] https://en.wikipedia.org/wiki/XHTML#XHTML_1.0
[7] https://en.wikipedia.org/wiki/CSS#Variations