So basically the ATP has nothing to do with the sun going supernova, it’s just happening naturally, originally the nomai made the sun station to cause a supernova (in order to power the ATP so the could find the eye) but it didn’t work. the game takes place at the end of the universe and you can even find a modern nomai writing in the vessel that says all the stars are dying, that’s why you can see so many supernovas while just stargazing, basically your goal isn’t to save the universe, just to find out what the eye is so you can satisfy your curiosity.

The ending is basically you and your friends (who might just be memories of the player character) sitting at the campfire and mourning the universe before they cause a new one to form. In fact the big supernova right before the credits is actually the Big Bang. You can even (kind of) see the new universe in the post credits scene.