It’s a problem with the mod_ssl package in RHEL8 and CentOS 8. When you install it the first time, it produces an invalid Apache configuration.
Supposedly, restarting Apache via systemd fixes it:
systemctl restart httpd
Beneath the hood, it causes the following command to run, which fixes generates the missing snakeoil certificates:
/usr/libexec/httpd-ssl-gencerts