That's not what happened here.

Nat founded Xamarin which was acquired by Microsoft in 2016. Github was acquired in 2018 and Nat was already an Microsoft employee at time.

So Nat departing now is actually 5 years post the Xamarin acquisition (when he joined Microsoft).

https://www.linkedin.com/in/natfriedman/

EDIT: what's also interesting is that Thomas Dohmke joined Microsoft in 2015, moved to the Github division around the time of the acquisition (2018) but only became CPO 4 months ago.