The first half of the IE6-9 era was part of a deliberate scorched-earth strategy to harm the open Internet, and the second half was them furiously backpedalling from that when it failed.
It wasn't a technical decision, it was cynical business strategy, and having their IE brand get trashed is the least of what they deserve. I'm kind of annoyed with how quickly people are willing to forgive them, considering what bad actors they've been up until recently.