None of the acquired companies were forced at gunpoint to sell to Github. Very few technology companies are created with the intention of being an ongoing profitable concern. If they are investor backed, almost by definition they are looking to be acquired. A statistical minuscule number of technology companies ever become profitable.
I would think almost every acquisition ever has been voluntary, among companies that aren't publicly traded. But we were talking about Github's/Microsoft's acquisition strategy. The companies being acquired don't drive that, even if they enable it.
