Cron scripts from the /etc/cron.<timeinterval>/ will run as root. Also, the error you're focussing on wasn't in the first error presented by @istler and is probably totally not relevant for this thread.
Well, that owner isn't root 
From Certbot-auto deployment best practices (as linked in the error you've posted):
Make sure that the directory path containing
certbot-auto(which includes every directory accessed in the absolute path tocertbot-auto) doesn’t allow writing for low privileged users.