May be you've forgotten FrontPage, a product acquired by Microsoft and then developped by Microsoft and widely promoted as part of Office, that insisted in declaring webpages as "ISO 8859-1" even if they contained characters that are only in "windows-1252". Even if we edited the page externally to correct it, FrontPage *automatically* changed it into "iso-8859-1".
So Microsoft has a responsability about this, even if the problem first appeared in Netscape browser (but at least Netscape accepted pages declared as "iso-8859-1" without problems, as well as web pages correctly labelled as "windows-1252". I perfectly recall the many support questions sent to MSDN about this Frontpage bug (and the many complains received by webdesigners using FrontPage, that their websites were bogous, and that these webdesigners were "stupid", "incompetent", never "read the RFC's" and so on...) Microsoft never published a correction in FrontPage, pretending that this would cause problems of interoperability (but interoperability problems were already existing at this time : only IE could then correctly display pages edited in FrontPage, Netscape at this time was only working in Windows, and on all other OS'es those pages were garbled) I do think that this is this FrontPage bug that created the proliferation of webpages incorrectly declaring the wrong charset, and that then forced all browsers to adapt. The Netscape bug itself did not initiate this proliferation (and Netscape was even corrected later without this bug, but then had to revert this correction due to the proliferation of incorrectly declared webpages).
