Congress directed the FAA--by law--to delegate certain aspects of certification to non-FAA entities. This directive was issued by H.R. 302 - FAA Reauthorization Act of 2018, 115th Congress.
Yes, the ODAs. I'm not making a value judgement that this is good, bad, or indifferent. I'm just trying to provide factual context to understand when and why the delegation of certain aspects of certification has occurred.
[1] https://www.congress.gov/bill/115th-congress/house-bill/302/...