The discipline vs. the platform
The CISSP certifies that a practitioner can think about security at the organizational level: risk, architecture, identity, operations, governance, independent of any vendor. It is the credential the market uses to gate senior roles.
The AWS Security – Specialty certifies that a practitioner can actually secure AWS: design KMS key strategies, tune GuardDuty and Security Hub, build least-privilege IAM, architect logging and incident response in AWS-native terms. It is the credential cloud teams use to gate AWS security work.