All the decisions related to cloud migration are driven by business requirements and effective Business Impact Analysis(BIA)and cost-benefit analysis

With compliance inheritance, the cloud provider's infrastructure is out of scope fora customer's compliance audit, but everything the customer configures and builds on top of the certified services is still within scope.
Reference: CSA Security GuidelinesV.4 (reproduced here for the educational purpose)

Information Bleed With multiple customers processing and storing data over the same infrastructure, there is the possibility that data belonging to one customer will be read or received by another.
Moreover, even if this does not happen with raw data, it might be possible for one customer to detect telltale information about another customer's activity, such as when the customer is processing data, how long the procedure takes, and so on.

The primary goal of whole business continuity and disaster recovery exercise should be health and human safety.