I have a noninformed thought on this... I think a lot of these issues are actually because they're not on modern Cloud yet.
I think GitHub was rolling everything themselves when Microsoft bought them. Ever since, MS has been working to strategically shift to Azure but that's a difficult and careful process that takes time.
In the meantime, the AI boom hit and usage went through the roof, crippling aging non-scaled infrastructure that hasn't had a chance to be modernized yet.
A lot of issues might very well be "we broke something while migrating", but I think a lot are also simply capacity issues on legacy.
None of that is true, sorry.
For someone the size of GitHub, the cloud is not infinite or infinitely scalable, and running their own datacenters is fine and completely normal and not at all "aging" or "crippled". Like the meme says, the cloud is just someone else's computer running in someone else's datacenter.
The traffic increases they cite as the reason are absolutely the reason. Those numbers are insane.