Most probably those services are started because some other service depends on them.
After running systemctl disable someservice the service someservice is not "disabled" in the sense that it can't be started, it merely isn't started automatically at startup. If you want to make a service not startable, use systemctl mask (or, you know, uninstall/delete it?).
systemctl list-dependencies --reverse mysql.service should list the services that depend on mysql.service.