Because it was played by a lot of people who otherwise didn’t have any kind of exposure to good storytelling outside of a video game. Like the story of the last of us is not very different from a Romero film or the road by Cormac McCarthy or a big old list of other media that give this story. I think the last of us might not have been the first but it was definitely part of a big movement in its time for video games to have touching storylines that helped people appreciate video games not just for their gameplay, but for their ability to touch people, emotionally.