Innovator's dilemma matters if you're actually making money from your current product. Skype isn't in any way material to Microsoft's revenues, but is an important mindshare property (and could tie in to other Microsoft tools; integration on WP and Windows desktops, etc.)
I beg to differ. Nowadays Skype is always inquiring people to convert their account to a Microsoft Account! The "Metro"/"Modern" version of Skype for Windows 8 even requires a Microsoft account.
Even if the mindshare isn't directly valuable to Microsoft, it's valuable to Google. Keeping Google from getting it should have been more important than squeezing every last penny out of Skype.
