Legitimate questions:
Many websites had to be specifically coded for IE as it wouldn't render correctly many basic parts of HTML/CSS.
Was IE6 demonstrably less compliant than other contemporary browsers? I recall - similarly - sites that were "Best viewed in Netscape Navigator at foo x bar resolution." Also Microsoft would unilaterally add proprietary features
IIRC, IE6 added XmlHttpRequest, which - though there were other workarounds to accomplish the same thing - enabled AJAX.Do not other browsers even today add their own features (e.g. browser-prefixed CSS properties) prior to standardization?
...and tie their software to it e.g. Outlook/Sharepoint
Okay, that's definitely bad.
Also Microsoft would unilaterally add proprietary features and tie their software to it e.g. Outlook/Sharepoint which then encouraged corporations to do the same as well. Apple actively participates in standards organisations eg. one for Web Components:
http://www.w3.org/2015/04/24-webapps-minutes.html