Earlier in the episode Nathan (mostly) successfully imprinted the behavior of a deceased dog on one of the owner’s clones by recreating the dead dog’s life as a puppy. So after reading Sully’s memoir, Nathan tries to imprint Sully’s behavior as a pilot onto himself by reliving Sully’s life.
It’s supposed to help people rehearse for some important event in their lives. He decided to do that but for airplane crashes. It goes off the rails (intentionally) but also brings to light stuff that would also probably improve airplane safety.
He got buy-in from a former NTSB member who appears in the show. In that same CNN segment the NTSB guy says he’ll be using what they learned to train people but Congress/FAA don’t seem interested thus far.