If it was failing slowly, why didn't they fix it then? Why didn't they notice?
Could it be because they fired all the people who know how to monitor and identify such problems? That's what SREs are for.
Please share the information you have which contradicts the conclusions I have drawn from Github's statement.
(And we know they're liars. They report very few of the actual incidents they have; see for example https://mrshu.github.io/github-statuses/)