Although you may believe that Microsoft 365 protects your data completely, that is not true. Most SaaS providers, such as Microsoft 365, protect your data against infrastructure-related threats but not from several major causes of data loss.
Like most SaaS application providers, Microsoft follows the shared responsibility model, which means you are solely responsible for the security and integrity of your data, endpoints, accounts and access management, as mentioned clearly in your service level agreement. This means that unintentional deletions, malevolent insiders, and other factors could wipe out your essential business data.