It certainly doesn't seem like either of those examples further your point. Both GitHub and Skype still exist as essentially the same core product they were at the time of acquisition, plus lots of new features which are clearly the results of substantial investment in the product by Microsoft.
GitHub was a complimentary product that fits into Microsoft’s strategy.
Skype was almost certainly some sort of scheme to kill Skype and bring lawful intercept to the platform. Skype at one point owned consumer voip globally.
