If you're interested in how other folks handle super important private keys, I highly suggest reading the IANA documentation on the DNSSEC Root Zone and how they manage that:
https://www.iana.org/dnssec/archive
https://www.iana.org/dnssec/archive
https://www.cloudflare.com/dns/dnssec/root-signing-ceremony/
I'm not blaming Moz, CACert were breaking new ground in trying to build a transparent process for a member-run CA. I believe they failed to find a suitable auditor that didn't cost a mint, and could work within the CACert transparency constraints.
Then LetsEncrypt came along... and ate their breakfast.