Two issues I see here.
1. People decrying developers writing apps to IE6/ActiveX/etc.
These developers write to the capabilities of the machine in front of them - expecting MS to continue to support them. Nobody performed an architectural review of the components/interfaces used prior to application deployment. The fact that the vendor was leading them up s**t creek is largely an MS issue.
2. Upgrades not performed.
Vendor upgrades are always carrot and stick to entice the customer to upgrade. MS has been unable to create an enticing enough carrot in all these years - so meet the stick. Customers have been warned for years about this potential - but never felt threatened enough to sign the cheque. We can only hope that equation is now somewhat rebalanced - at least for the short term.