actually, I think this time it is the other way around, Azure is more the solution than the problem.

Github in the past ran on their own Hardware. That is fine, if your load is predictable and nto changing rapidly. However, the evolution of the past few months/years has shown, that the previous assumptions about growth are now outdated and scaling that capacity on your own metal is not that easy. Hardware has lead times of many weeks, especially in the current situation, datacenter capacity is even longer and more difficult, especially right now.

Choosing not to deal with scaling the hardware is a valid choice in this situation. Yes, Azure is a bunch of servers held together with glue, duct tape and a lot of hope, but I think, the github hardware is not much better at the moment.