To me, "dead" means something like "checkmated". "X is dead" means that X is in a situation that it can't get out of. Can you please point me to your definition?
Yes that is it. Microsoft as the bogeyman of the tech industry (i.e. a factor one must consider). That concept is "checkmated"/dead. It no longer holds true. And there's nothing immediately obvious MS can do to reverse that situation ("get out of it").