My understanding is that Mozilla is primarily just a sponsor of ISRG, the non-profit behind Let's Encrypt. Some of their sponsorship includes dedicated engineering time, but LetsEncrypt still has to pass all the same audits and requirements as any other CA, as defined in the Mozilla CA Certificate Policy at https://www.mozilla.org/en-US/about/governance/policies/secu....
Mozilla's not a nepotist with regard to its root store. :-)
Mozilla's not a nepotist with regard to its root store. :-)