Yeah “how this logic flaw occurred” is the wrong question.
How a common bug was rolled out globally with no controls, testing, or rollback strategy is the right question
How a common bug was rolled out globally with no controls, testing, or rollback strategy is the right question
And then absolutely the release process.
Rollback is hard I guess once your OS can't boot.
This is why the client needs have enough error handling to realise it's latest update has now caused unsuccessful boot and roll that update back locally to the last known good configuration (or completely back to factory and pull all updates again).