Jimmy made a promise to his boss John Dutton previously in the series with a lot of turmoil, and he broke that very marked sacred word in season 3- end.
He later broke his promise after being compelled by his love interest Mia and then rode the horse.
This illegal action had him deemed ill fate as he was tossed to the ground by his ride.
He broke his back, and season 4 showed him to survive the event but still broken to a vulnerable state.
He broke his considerable promise with his boss John Dutton and thus, already made him a manageable attack threat to the mob.
The series also has indicated earlier about the sad endings of everyone who has ever cut John’s marked words.
