Blizzard has long been derided for its poor performance when handling massive player events, showing worse performance in that regard than large private servers such as Nostalrius.
The biggest technological advancement in the past couple years that could help explain their sudden and dramatic improvement is AI, in my opinion. I think it's fantastic if AI is indeed a large part of the reason for their rapid improvement.
Lets agree to disagree, happy to attribute llm wins where respect is earned but not more, to balance out various horror stories