A resource group is a logical container for Azure resources. When you create a resource group, you specify which location to create the resource group in. However, when you create a virtual machine and place it in the resource group, the virtual machine can still be in a different location (different datacenter). Therefore, creating multiple resource groups, even if they are in separate datacenters does not ensure that the services running on the virtual machines are available if a single data center fails.
https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/overview#resource-groups