As the common user does not have to have the MFA to access, except the administrator role user in the Entra ID organization/Tenant, the MFA can be disabled as default.
Security defaults is being turned on as the default of M365 Tenant setting.
To disable the MFA by default for all users, the Security Defaults must be turned off.
Even if the Security Defaults is turned off, the user who has administrator role assignment in Tenant keeps the MFA getting turned on.
Step
Go to M365 Admin Center.
Identity -> Go to Identity console.
Overview -> Properties.
Go to bottom of the configuration items, and “Manage Security Defaults”.
Change the setting to Disabled in dropdown list and select one suitable reason for this setting.
