This show was ruined by J.J. Abrams "Mystery Box" nonsense
The first couple of seasons got off to a great start but after that it was just adding mysteries for mysteries sake and it was clear that they were just making it up as they went along with no sure idea of where they wanted to take things. Then it came that they had to wrap things up and came up with he most lazy/absurd ending. They couldn't get out of the mystery box they had boxed themselves in.
Abrams is a hack who uses "mystery" as a substitute to his lack of talent.