Because the authorization check happens inside the Entra service, not ARM. Only Microsoft backend engineers can resolve this. This requires a Microsoft Support backend ticket routed to Microsoft Entra ID/CIAM Engineering Backend Directory Provisioning Team. It looks like you are using a Microsoft Personal Account, and Microsoft no longer allows MSAs to create Entra tenants. However, there's no need to worry about creating a tenant just to open a subscription support case. Remember, support is linked to the subscription itself, not the tenant.
How To Open a Support Case Without a Tenant
Since portal support is failing to load, follow the steps below:
Open
https://portal.azure.com/#view/Microsoft_Azure_Support/HelpAndSupportBlade
If that fails, use
https://azure.microsoft.com/en-us/support/create-ticket/
Sign in with your Microsoft account tied to the subscription.
Select --> Issue type: Technical
Service: Microsoft Entra ID
Problem type: CIAM
Severity: Minimal (or higher if blocking prod)
If Entra ID is not selectable, choose:
Service: Subscription Management
Problem type: Other
Explain clearly that a CIAM directory ARM resource exists without a provisioned Entra tenant and requires backend removal.
I hope this works.