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.

There are many things which run well on Azure - built by companies with good dev teams.

https://trends.builtwith.com/websitelist/Microsoft-Azure

Plenty of crappy websites on the list too.

or rather the slowness problems of MS has nothing to do with hardware or infrastructure limitations. You cannot just throw infra at a problem to mask poorly written code beyond a point.