You say that as if github never has outages when the reality is, like any large service, it has frequent service outages.

Just check the github status pages, there are orange level issues almost weekly and you don't need to go back too far for full outages.

Because GitHub is so stable and never goes down?

No service is perfect and github has had plenty of outages. They will only become more reliable with the resources of MS/Azure at their disposal.

Having worked in big Azure customer I wouldn't say resources equals stability. The reality is more resources + quality engineering + failure testing.

As this case tells, Azure, isn't spending a lot on failure testing. Also, having experience with being an big Azure customer, I can tell you that things look better than they are.

Small Azure customer (five figures a month), but can co-sign all of this.

Azure looks shiny from the outside but we've had way, way more problems, from uptime to bad APIs to awful language SDKs to bad user interfaces to licensing hell, than I've ever had on AWS or GCP. It's so bad that I am currently weighing whether or not to advocate for a migration off of it, at nontrivial expense, because I cannot pretend to provide reliable services for our customers.