A DDoS attack is often used to distract a company's security team. While the security staff is scrambling to get the website back online, the attackers use the chaos to conduct a more serious, stealthy attack.

I don't doubt there will have been sporadic examples of this, but what points to this "often" being the case? It seems like a tactic that wouldn't often pay off, since DDoS mitigation rarely involves relaxing security systems

Mistakes can be made during reconfigurations but you'd have to catch those while the issue is still live. Sounds like an advanced threat actor and not the run of the mill ransomware people (not that they're necessarily unsophisticated, but why'd they bother with these odds when there's low-hanging fruit to reliably exploit)

It was interesting to read that the record breaking attack caused no glitch whatsoever in the service MS provides. Which is so slow normally that I start to wonder if that is a strategy, having headroom for these kind of situations, no-one realizes slowdown when it is already slow. ;)

This is just a crazy thought, tangential to what are happening during an attack.