Fuck AI

No, that is required for rm -rf /. But the command in question was rm -rf /*, note the asterisk. The * will be expanded by the shell, so what rm sees when it evaluates argv is not /, but [/bin /usr/ /lib ...].

You can test this yourself. Run: rm --recursive --interactive /. It will abort, saying:

rm: it is dangerous to operate recursively on '/'

rm: use --no-preserve-root to override this failsafe

Then, run set -x in your shell. That way your shell will print the command that is actually executed. Finally, run:

rm --recursive --interactive /*.

In my case, the output is:

$ rm --recursive --interactive /*
+ rm --recursive --interactive /bin /boot /dev /efi /etc /home /lib /lib64 /media /mnt /opt /proc /root /run /sbin /srv /sys /tmp /usr /var
rm: remove symbolic link '/bin'? 

The line starting with a + is from the shell and shows which command was actually executed. After that, you can see rm will now happily start deleting files.

Apparently the root directory protection was only added in 2018. Rm can be also configured without the root protection. Unsafe configurations or out of date software would allow this.

Yes, this should have been prevented by the --preserve-root option, but that didn't happen. No catastrophe is ever the result of a single point failure.