The souls genre
FromSoftware became famous for Demon's Souls and Dark Souls, where you die often and learn from your mistakes. Boss fights are hard but fair. The name gave rise to a whole genre, the “soulslike”.
An open world
Elden Ring gave players freedom: when a boss is too hard, they can go elsewhere, get stronger and come back. As a result, even people who had been afraid of the genre finished the game. It has sold tens of millions of copies.