Does CMMC Level 1 require multi-factor authentication?

Short Answer

No. Multi-factor authentication is not one of the fifteen CMMC Level 1 requirements. It is a Level 2 requirement under NIST SP 800-171. Level 1 asks you to identify users and verify their identity before access, which unique accounts and passwords can satisfy.

What Level 1 does ask for on identity

Two of the fifteen requirements cover identity. Identification, IA.L1-b.1.v, is about telling users, processes, and devices apart. Authentication, IA.L1-b.1.vi, is about verifying that identity before granting access. Neither one names MFA.

Other things people think Level 1 requires but it does not

None of these is a Level 1 requirement either. A System Security Plan is required at Level 2. A third-party assessment applies only when a contract calls for Level 2 (C3PAO). The FedRAMP Moderate condition applies to cloud services that process, store, or transmit CUI, and no CMMC level names GCC High or any other product. MFA is a strong control, and many small suppliers use it anyway. It is simply not one of the fifteen you are assessed against at Level 1.