I mean that makes sense no? Attacks like that rely on compromised servers so it shouldn't be a big surprise large hosting provides are among the biggest attackers. Other large ISPs like digital ocean and Alibaba are among the top attackers in that attack also.
I assume this attack is UDP based unlike the one you linked too.
People aren't paying with their own money for DDoS machines normally. Well, maybe there are some small operations like that. But often the traffic comes from a hacked service that's a part of a bigger botnet. It may lead to a larger detection ratio on AWS/GCP, but the attackers are not paying the costs.
Attackers aren't paying with their money, but it's important for them to go undetected. If your bandwidth is a fixed cost (ie isn't related to your actual usage) you are much less likely to keep an eye on it than if it costs an arm and a leg.
I assume this attack is UDP based unlike the one you linked too.