Different functions, both senior
The CISSP is designed for security practitioners — engineers, architects, managers, and CISOs whose primary job is designing, operating, or governing security. Its eight domains cover the full lifecycle of building and running a security function.
The CISA is designed for IT auditors — professionals whose primary job is independently assessing, testing, and reporting on the effectiveness of IT controls, systems, and processes. Its five job-practice areas cover the audit process, IT governance, systems acquisition and development, operations and resilience, and protection of information assets. The audit lens is fundamentally different from the security operator lens.