Because she was using the bulk of her power to seal the demon that our enemy had unleashed upon the world. If she hadn't contained it, then there would not have been a future to send us to. It broke her to make that choice, but she gave us a future.

[She listens patiently to the questions, finally holding up a hand.]

Slow down, one question at a time. I'll start with the last. Usagi Tsukino is my friend. Her story is hers to tell in her own time. Not mine.

[Which is true.]

Just...breathe though. I'll explain, but slow down.