Because he came to bare witness to the truth, to show us the way, his life is the life, he preached the gospel of salvation, and he overcame Satan. And because he has overcome Satan and the world, he can give those who have faith in him strength to overcome him too by the spirit. And if we believe in him, and have faith then by the grace of God we will be blessed with Gods holy spirit and he will save us daily from Satan.
Jesus brought us a new and living way, and once we believe in him and have faith and are blessed by the spirit, then he should be strengthening us to turn from sin, to deny temptation and bare our cross and the the more we die, the stronger we grow on the spirit and the more Christ increases in our hearts.
If Jesus had of given in, and had he not have bore his cross and he hadn't suffered everything that Satan threw at him, then he wouldn't have overcome him and Satan would have won. Jesus had to bare it and overcome Satan with love, love is the key. The love of God overcomes the sins our flesh, because if we truly love God, and he us in our hearts then we will deny ourselves and Jesus told us that if we truly follow him, then we will bare our cross and trust in God and keep our faith through our tests to the end and obey God. The way is narrow to life, and only few will find it.
If Jesus hadn't have come and bore witness to the truth and denied Satan and this world. Then we would never have known the true way back to God. And there is only one way, and that is the way of Christ Jesus because he is the only way the only truth and the only life and the only one who has never sinned and showed a us a perfect example to follow.
Right I'm off to clean