Their success blinded them to the fact that mobile and tablets comprised a completely different functional and experiential environment, and so they kept pushing a “Windows everywhere, Outlook everywhere” strategy that failed to create a smartphone market they initially owned, failed to take advantage of the business mobile market Blackberry created, failed to take advantage of the premium consumer mobile market Apple created, and failed to take advantage of the mass consumer mobile market Android created (despite their last bite at the mobile OS apple — so to speak — being quite good).
Nothing breeds failure quite like success even, evidently, in hindsight.