Because then if you losed ur crown then you had no power over ur people and because then the crown had too much value to just give it up so they discoverd the bomb and blew up the greed mountains but... (the lore bettwen the years) after the monarchs death the crown was sealed for good into the old caves to not be dangerous anymore and they saw that the greed wasn't really looking after the humans but after the crown itself, and because the crown was sealed the greed was sealed too so that the world will live in peace again (the lore still dosen't says how the greed appeared or why they want the crown so much but this is enough story for now... )