Why is it that CTAP2 can be used for passwordless authentication, when U2F can't?

Many blogs ([like this one](https://www.okta.com/blog/2019/04/the-ultimate-guide-to-fido2-and-webauthn-terminology/)) say:

> CTAP1 is an older standard where the external authenticator is expected to be able to provide the second factor of authentication. CTAP2 allows the external authenticator to be used as both a first and second factor of authentication and eliminates the dependency on passwords.

Is this true, and if it is true, why? What does CTAP2 have that CTAP1/U2F doesn't, that enables passwordless authentication?

authentication cybersecurity passwordless passwordless authentication u2f