why my all saved logins where removed
Help me out how to recover all my logins
What about the rest of your profile? Settings, bookmarks, history, passwords . . . .
Do you know how you lost the data?
Firefox 80+ has a logins-backup.json file in the profile folder that can be used in case of issues with logins.json or to undo an accidental delete of a login, so you can check if you can find this file in the profile folder or in a backup and replace the current logins.json. Make sure to keep a backup copy of all involved files (logins.json and key4.db and logins-backup.json)
You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.
Help -> More Troubleshooting Information -> Profile Folder/Directory: Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
If you use a Primary Password then you can prevent losing passwords by canceling the PP prompt. You need to logout beforehand by canceling a PP prompt, e.g. by clicking the eye icon in Lockwise (about:logins).