::: spoiler spoiler Up until that point many players will have thought they could stop the supernova, that they could save everyone, they thought that was the point of the game, how you won. To then be faced with the fact that there is no stopping it and that the star has just reached it's end. It's like getting a bucket of ice water dropped on you realizing that there is no saving anyone, everyone will die, this system will be destroyed, this universe will end.
Accepting that end is hard, but I think the ending showing that all ending are also new beginnings, that everything is built on what came before goes a long way to letting people be ok with it.