I think it's most likely a little of both. It seems like the fact most systems failed at around the same time suggests that this was the default automatic upgrade /deployment option.
So, for sure the default option should have had upgrades staggered within an organisation. But at the same time organisations should have been ensuring they aren't upgrading everything at once.
As it is, the way the upgrade was deployed made the software a single point of failure that completely negated redundancies and in many cases hobbled disaster recovery plans.