Unexpected result of Nginx - nginx

Question

I've a server with 2 services on it. Software are Ubuntu20.04 OS, Nginx and certbot.
So, then I check nginx status:
~$ sudo systemctl status nginx.service
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; disabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2021-12-13 10:48:55 CET; 35min ago
Docs: man:nginx(8)
....
des. 13 10:48:55 u nginx[248435]: nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
des. 13 10:48:55 u nginx[248435]: nginx: [emerg] still could not bind()
des. 13 10:48:55 u systemd[1]: nginx.service: Control process exited, code=exited, status=1/FAILURE
des. 13 10:48:55 u systemd[1]: nginx.service: Failed with result 'exit-code'.
des. 13 10:48:55 u systemd[1]: Failed to start A high performance web server and a reverse proxy server.
and checking of configuration:
~$ sudo nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
But at the same time both services are up and working as they should. If I ask about nginxs' processes, i've next
~$ sudo ps -ax | grep nginx
245336 ? S 0:00 nginx: worker process
245337 ? S 0:00 nginx: worker process
245338 ? S 0:00 nginx: worker process
250704 pts/7 S+ 0:00 grep --color=auto nginx
and check one of them (it doesn't matter which one)
~$ sudo systemctl status 245336
● snap.certbot.certbot.***********.scope
Loaded: loaded (/run/systemd/transient/snap.certbot.certbot.***********.scope; transien>
Transient: yes
Active: active (running) since Mon 2021-12-13 09:39:30 CET; 1h 35min ago
I can't imagine what happens and why it works in this way. Before this problem, I updated certbot and deleted a few certifates (they were expired and unused).
Who can explain me how it's work? And why are the services up?