One of the questions we could ask is, "why?" But I'm more interested right now in looking at what that it means for us. Perhaps in this way we can also see a little bit of one of the reasons as to why.
In order to create an environment in which each person truly has free will to choose HaShem's Torah, the choose life, HaShem had to hide Himself. There are many levels and many ways in which HaShem hides Himself. First and foremost is that He constricts His light in such a way that we experience darkness, both on a spiritual and a physical level. This step wasn't enough in and of itself, rather he created spiritual forces that pull us in directions opposite to HaShem's will. In such ways he creates a vaccuum, we feel the pull of our natural desire to do HaShem's will, and the pull of our yetzer hara to go against HaShem's will. Right there, in the middle of these to competing forces, we have an area of free-fall, an area of free will. We can choose whether to reinforce our positive or our negative desires. We rule over both of them and they don't rule over us.
The Satan, (S"M as he is called) is the collective total of all those forces that pull us away from HaShem's will. He tries to break down and pull under any person who might try to raise themselves up in the service of HaShem.
What happened with Esav and Yaakov? Why did Yaakov merit to receive the blessings of his father? Esav was the more powerful, Esav had far more potential than Yaakov, so logically the Satan bent all his effort and all his will to seduce, beat down, and destroy Esav. Yaakov, who held himself humbly and made himself seem unimportant was no threat, and therefore of no interest to the Satan.
Realize what this really means. Even if the Satan knew about Yaakov Avinu's potential, if he neglected Esav and worked whole-heartedly to depose Yaakov Avinu, Esav could have become a Tzaddik and the Satan would not have had the power to stop him. In such a way, the Satan must always confront the greater and more powerful threat and neglect the lesser threat who makes himself small.
This is the greatness of HaShem that reveals His humility. The world is created such that only those who make themselves small and humble can succeed at connecting to HaShem. That success will also inevitably overcome the Satan. Since the Satan's great power is spent on knocking down those who try and raise themselves up. Through this system HaShem ultimately knocks down the Satan who raises himself up.
Evil cannot win. ever. This is the kindness of HaShem and the system which He created, to allow us individual souls to choose between good and evil, to play our part in the epic saga of existence. Through our choices we show our true colors, it becomes clear where we put our faith.
On the high level everything is preordained, on the low level, we get to choose sides and our ultimate fate.
Yaakov already beat Esav, Mosheh already killed Bilam, the Torah has already been given, Eretz Yisrael has already been given. Our choices and our actions determine whether we side with Yisrael, Mosheh, and Torah, or whether we choose death.
Since the real choices are only in the lowest of places, that is where you find HaShem's greatness, that he gave us a real choice to act as independent creations.