Actually, man was created to kill Satan. In heaven, there are really just concepts and ideas. You can't steal anything or kill anybody up in heaven. It's basically talk. So in order for God to make Satan put his money where his mouth was, he created the physical universe and creatures with free moral agency, who would be given laws to obey and the penalty of death if they sinned. this was an opportunity for Satan to be the manslayer he always was. God gave him the opportunity to kill billions of men. That was something so much of a high to Satan that it was worth dying for.
He had a golden chance because of God's pronouncement, which said specifically, "IN THE VERY DAY you eat of it, you will die." Now that seemed like God was saying the punishment would be speedy. If Adam died the very day he ate from the fruit then he would die with all of his billions of potential offspring. They would be all killed. Satan would have a big victory!
Adam was likely around 30 years of age when Eve was created, prompting him to say, "At last, bone of my bone and flesh of my flesh." Adam was a typical black man, beautiful in form, not that bright. Eve was stunningly beautiful, white, of course. So Adam was overcome with delight with this new wife. When she ate of the fruit, he couldn't deal with that and so actually preferred to die with her. That's not new. Lots of lover's think they would rather die than live without the person they love. Adam, of course, knew what he was doing. Satan was delighted and glad to die as well, having killed off billions of persons that God and Christ already loved.
But then God flipped the script on Satan. He basically said: "Oh, you thought I meant a 24-hour day? Oh no, I meant a 1000-year day!" It meant that Satan would essentially kill few more than who Jehovah was going to have to kill anyway. The righteous ones and the innocent ones would be saved via the ransom sacrifice. So Satan's murderous "high" was short lived.
Bottom line is, the Edenic scenario was a trap set up to destroy Satan and it worked. Satan took the bait and now he is going to end up dead throughout eternity. In the meantime, the heavens will be restored to a peaceful and beautiful place without Satan's constant nagging and resisting.
Because it was through mankind that Satan was able to be excised from the universe, some of them were given great glory, to become angels, more glorious than any of their angelic brothers. Those new spiritual beings would be married to Christ, who is Michael the archangel. So Satan is insulted again. Impressed with her own beauty corrupted her, now someone far more glorious and beautiful would be in heaven.
All Satan has left is to kill as many humans as he possibly can. That is his legacy. But it is not all that grand because all the favorites of God and Christ from mankind were saved from Satan's murderous attempt.