Windows 11 systems must have a Trusted Platform Module (TPM) enabled.
Credential Guard uses virtualization-based security to protect information that could be used in credential theft attacks if compromised. There are a number of system requirements that must be met in order for Credential Guard to be configured and enabled properly. Without a TPM enabled and ready for use, Credential Guard keys are stored in a less secure method using software.
How this relates to the STIG checklist: STIG vs SCAP benchmark.