The GCP move was decided upon months before Microsoft acquired GitHub[1].
[1]: https://venturebeat.com/2018/04/06/why-and-how-gitlab-abando...
[1]: https://venturebeat.com/2018/04/06/why-and-how-gitlab-abando...
Call me a tinfoil nutjob, I still don't buy it and would move away from azure too in that situation.