Safari stopped working and won’t reopen.

Same issues. There are several threads open with same issue.

https://discussions.apple.com/thread/251220745

https://discussions.apple.com/thread/251239079

https://discussions.apple.com/thread/251221446

https://discussions.apple.com/thread/251213669

https://discussions.apple.com/thread/251224063

Tried with no luck: Cleared caches, history. Disabled extensions. Deleted cache files (for WebKit & Safari).

What works: Logging in as a clean user. So there's some conflict with latest security updates and something in Safari at the user-level.

Try launching Safari with the shift key held down. This will open Safari without restoring the tabs you had open.

If that does not work, shut down the computer. Reboot it with the shift key held down until you see the Apple logo. This will boot into Safe Mode. See if the issue still occurs then.

Are you running any anti - virus programs? Using a VPN?

Try setting up another admin user account in System Preferences/Users & Groups to see if the same problem continues.

Isolating an issue by using another user account    https://support.apple.com/en-us/HT204443

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. If the log won’t post, try posting it in Pastebin and provide a link in a reply. After pasting the report in a PasteBin page, go to the top of the page, and copy the address in the URL bar. Paste that in a new reply.        Pastebin.    https://pastebin.com/

Etrecheck – System Information.      https://apps.apple.com/app/etrecheck/id1423715984?ls=1&mt=12

Web site version if required.  https://etrecheck.com