The FAA certified a plane that had a single-point-of-failure flaw that could crash it unless the crew was very aware of the flaw and procedures for surmounting the problem. Having certified it with that flaw, they didn’t require crew training on how to deal with the problem. When the problem manifested itself in the form of two crashes and hundreds dead, the FAA dragged its feet about pulling the plane from service, only doing so until every other aviation body had acted.
The FAA has acted like it works for Boeing throughout this mess, and it doesn’t seem to have learned anything from that. Hindsight? I wish the FAA had some.