Is there an "explain like I'm 5" intro to FIDO2 that explains how FIDO2 as the single factor is more secure than the user entering username (not password) and t

Is there an "explain like I'm 5" intro to FIDO2 that explains how FIDO2 as the single factor is more secure than the user entering username (not password) and then using a CTAP1 token? (Also, how do you log in to multiple accounts on the same service with FIDO2?) How many usernames can a Yubikey 5 remember in the FIDO2 mode? CTAP1 requires no storage beyond a token-wide counter.