The main argument about XHTML not being "lenient" always centred around client UX of error display - Chrome even went on to actually implement a user-friendly partial-parse/partial-render handling of XHTML files that literally solved everyone's complaints via UI design without any spec changes but by this stage it was already too late.
The whole story of why we went with HTML is somewhat hilarious: 1 guy wrote an ill informed blog post bitching about XHTML, generated a lot of hype, made zero concrete proposals to solve its problems, & then somehow convinced major browser makers (his current & former employers) to form an undemocratic rival group to the W3C, in which he was appointed dictator. An absolutely bizarre story for the ages, I do wish it was documented better but alas most of the resources around it were random dev blogs that link rotted.