Earlier quoted context omitted.
Don't forget MSN Messenger was discontinued/merged into Skype. So they fucked it not once, but twice. Literally handed over their dominant position in instant messaging for nothing.
Wait - what about MS Lync/Office Communicator? I don't remember if that was just a branding change of "MSN Messenger for Business" about the time right before the Skype acquisition, or folding in (and failing with) yet another IM/Video chat solution. So should the count actually be three?
Honestly I think they simply don't care, and from their perspective they finally have gotten it right with Teams.