Why does the wildcard SSL certificate point to a different domain on the server?

Question

CentOS

I install the certificate according to this scheme:
https://habr.com/en/post/354052/
Everything seems to be going smoothly, at the end I get the following message:

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator dns-cloudflare, Installer None
Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
Obtaining a new certificate

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/site.ru/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/site.ru/privkey.pem
   Your cert will expire on 2020-06-13. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

But when I go to the site's subdomains:
Firefox does not trust this site, because it uses a certificate that is not valid for moskva.site.ru. The certificate is only valid for the following domains: site1.org, www.site1.org

Answer 1

If you issued a wildcard certificate for site1.org, then it is strange to expect it to work for site.ru