> Any competent IT team has backups

Backups can be sabotaged (turned off or schedules manipulated) or compromised (say, by lateral movement).

> Even if everything was hosted on Instructure's infrastructure, it's all AWS.

AWS Backup isn't foolproof. Get your hands on administrator credentials as an attacker and suddenly the only thing between everything being gone for good and unrecoverable even for AWS is remembering to have put a permanent deletion protection on all resources in AWS Backup.