How hard can it be to understand this? If the Jinchuuriki is killed then so is the biju. But the biju eventually comes back in some form. The fox lent Naruto the chakra so that neither the host nor the demon would die. Minato sealed the kyubi into Naruto instead of Kushina because she was going to die, and Minato did not the Kyubi eventually coming back as well as Konoha being left without a Jinchuuriki.