What processes do you rely on to address risks from rogue cloud tenants that the security team doesn’t have visibility of?

I do not agree to @Adel Awad, it's not the Security that has to have the right to create new infrastructure in the cloud, but there has to be one dedicated and responsible team for the environment.
Architects build systems and services
Infrastructure team build templates for the container or cloud services
Security approves that
DevTeams just use templates and are not allowed to define their own infrastructure
CI/CD is an automated one-way street to PROD and the only way into it.
No interaktive service in PROD, if there is an error in PROD, fix it in DEV and start CI/CD

You need to lockdown your cloud environment so that only the cybersecurity team is allowed to create an environment under your domain ownership, you also need to monitor the attack surface , such as storage buckets exposed to the outside world , lack of conditional access , etc… there are solutions that helps you monitor cloud security (Cloud Security Posture Monitoring)