I think part of is that the CAB (the browser group setting standards for CAs) is much of the same people that initially supported Lets Encrypt, and also use Let

I think part of is that the CAB (the browser group setting standards for CAs) is much of the same people that initially supported Lets Encrypt, and also use Lets Encrypt as a justification for tightening requirements on other CAs. They really do _not_ want to be seen to be giving Lets Encrypt special treatment because of the connection between the CAB members and Lets Encrypt and the threat that Lets Encrypt poses to the business models of the traditional CAs. So a violation of the rules by Lets Encrypt is being dealt with by the letter, even when the issue clearly does not warrant that level of reaction. (See also the time Google Search banned Google Chrome from results for a month when one of their advertising campaigns breached the rules for paid SEO)