Are you kidding? Why did Jesus have to die? He had to die to offer up his perfect, childness body for the inherited death sentence upon Adam's chidlren.
Furthermore, Adam understood precisely what he was doing. He made q choice. He chose to worship and love his wife more than God. That was his choice. It cost a lot.
But underlying Adam's fall is who else got the death sentence, namely, Satan. The test was really a test for Satan. To see if Satan could resist killing billions of innocent people. He couldn't after it was all over. Satan ws frustrated, particularly since the creation of man.
You see, after Adam was created, Jesus, who is Michael the archangel, fell in love with him, that is, with mankind. God recognizes this special love Christ has for mankind by allowing his new wife to be chosen from those among mankind. So you have an angel marrying humans, basically, only the humans, of course are converted to angels. But his new wife essentially takes the place of his old wife. His old original wife was the most beautiful angel in all of heaven, whose beauty corrected him/her. Christ's love for humanity likely pushed Satan over the edge. How could Christ prefer a human, which was no more than an animal to Satan, over him, the most glorious angel in heaven?
So when a chance to kill Adam came up, along with all his offspring, he knew Christ would be devastated and that felt good enough a cause to die for. So Jehovah sort of arranged a window of opportunity for Satan to destroy mankind, but in the process Satan destroyed himself. In the end, Christ's love, mankind, becomes his new but true wife in heaven.
But that reflects on the personalities of Satan vs. Christ. Christ is a kind of down-to-earth kind of person. Even when he was human, he liked hanging out with "real" folk, prostitutes and tax collectors. He didn't like those who were self assumed and haughty and liked being the important ones in the room. Christ found mankind so beautiful and charming, he just couldn't help fall in love with him. this totally pissed off Satan, of course, so Satan tried to get revenge by killing Christ's "new love." Satan didn't care it would mean his/her death, since he was frustrated anyway. He probably figured God would devise a way to kill him off one day anyway or cast him into prison, so why not die a grand death with a grand finish. Kill off the beloved of the Creator and his favorite son who refused to join Satan's rebellion. That is what Satan thought he was doing, until God mentioned that, "Oh, BTW, when I said 'In that very day you shall die," I didn't mean a 24-hour day? Is that what you thought? Oh, sorry. I meant my 1000-year long day."
So in the end, Christ and Satan get divorced and he gets to marry his new love, lots of mankind. And everybody lives happily ever after without Satan around.
Why did Christ have to die? He had to die as a perfect, faithful, human so he could save mankind. Many of whom (1,440,000) he will actually marry; his new wife replacing his old wife, Satan.