The finale of the 19th century Yellowstone prequel killed off its most important character, but many viewers still wonder why Elsa dies in 1883. While the death is tragic, it is necessary to move the story of the Dutton's forward and to set up the world of 1923, Yellowstone, and beyond. Elsa Dutton (Isabel May) is the daughter of Margaret (Faith Hill) and James Dutton (Tim McGraw) — the founders of the Yellowstone Dutton Ranch. While it was sudden and shocking, the build towards Elsa's death begins when she is shot with a poisoned arrow during an attack on the caravan.
https://screenrant.com/1883-season-1-finale-elsa-dutton-death-explained/