A good reminder that if you want to use Apple Passwords as a 1Password replacement you need to export a static backup (and this must be automated). The Cloud is where data goes to die.
A found a relevant 2016 Apple Discussion post which would be Mojave era. So I wonder if it's a Mojave bug. The fix there was from "Linc Davis" a "Level 10" with 209K points 
Please take these steps to resynchronize the iCloud keychain. Your keychain on iCloud and your other Apple devices won't be affected. Take Step 2 only if Step 1 doesn't solve the problem.Step 1Back up all data.Open the iCloud pane in System Preferences and uncheck the Keychain box. You'll be prompted to delete the local iCloud keychain. Confirm—the data will remain on the servers. Then re-check the box. Follow one of the procedures described in this support article to set up iCloud Keychain on an additional device. Test.Step 2If you still have problems, uncheck the Keychain box again and continue.Triple-click the line below on this page to select it, then copy the text to the Clipboard by pressing the key combination command-C:~/Library/KeychainsIn the Finder, selectGo ▹ Go to Folder...from the menu bar and paste into the box that opens by pressing command-V. You may not see what you pasted because a line break is included. Press return.A folder named "Keychains" should open. Inside it is a subfolder with a long name similar to (but not the same as) this:421DE5CA-D745-3AC1-91B0-CE5FC0ABA128The above is only an example; yours will have a different name of the same general form. Drag the subfolder (not the Keychains folder) to the Trash.Restart the computer, empty the Trash, and re-enable iCloud Keychain.
Toggling Keychain off and on didn't seem to do anything so I figured I'd check in the morning. Before I checked though I did review my passwords in Monterey. For *reasons* (this happens way too often) I had to reenter my iCloud credentials there but I was also asked the usual iCloud keychain questions -- provide passcodes for my other machines.
Then I looked at my Mojave machine and Safari had my passwords again.
Maybe the fix was toggling Keychain and waiting a bit, but I'm suspicious that something happened somewhere in iCloud that required me to do the iCloud Keychain authentication dance from a Mac -- and Mojave couldn't do it.
Again, if you use Apple Passwords as your sole repository you need a non-iCloud backup.
- fn -
 No profile info, has participated in 97K threads. Either insane or an Apple staff pseudonym.