Honestly still insane to nuke a high-volume client's business after a single payment issue. There would be no reason for Google to believe that a single hiccup like that is evidence that they won't get paid and have to cut account access immediately.
Railway might not be even in the realm of high-volume clients for Google. For all we know they might be efficient in utilizing Google infrastructure.
But most likely, it's just automations in place without an appropriate human override coupled with gross negligence.