Keeping it basic today.
Back when I was younger, when I was first trying to figure out what made people tick, I started with the certainty of the will to survive. You understand that; it takes very little imagination to put yourself in a position of mortal danger and know that you would try to get through it alive. This quickly brought me around to Nietzsche, and I still don't know why people separate the will to live and the will to power.
Think about investment for a second.
Imagine that you're a primitive human having to trek down a grassy, sloping cliff to a stream to get water. You make this trek daily, and you realize that it's dangerous; you often slip a bit, occasionally fall, and know that you could get seriously hurt if things go just wrong. No medical care, predators everywhere... the situation just sucks. So one day, down at the stream, you look back up and realize that if the slope had less grass and more flat spots, you could climb up and down easily, carrying water in jugs, with much less danger. So you spend the next few hours with some primitive tools, hacking out the slope, and create a staircase out of rock and earth.
Totally economic activity. This investment of a few hours of your time reduces the level of effort you need to perform a basic, necessary activity, and will save not only more time in the future than what has been put into it, but it will lessen the degree of risk associated with it. And in making these changes, you've altered the natural world into something built for human use. You've brought it under your control. You've maximized chances for survival. You're not reacting, you're acting. This is empowerment. Is there anything more rational?
There's no reason to believe that such drives only apply to the strictly physical environment, by the way. The social environment is far more important now, having physically bent the world to such a high level of submission. The most unpredictable and dangerous factor we deal with is other people, so there's no reason at all - except for one's desire to see it differently - to think that the will to control people is any different from the will to control the physical world. The perspective that tells us otherwise is the result of an individualist culture built on philosophies that worked themselves out dialectically, proverbial knives to each other's throats, forcing us to talk out our issues until we come to an agreement which can be called a consensus. No matter how powerful you are, other people are still dangerous, and the myth of equality is built on a respect forced on one another in the same way a hurricane forces you to respect it.
But if people are often the only dangerous thing, they are just as often the only really valuable thing, and the question becomes one of the arrangements between the individual and the group, the questions of trust. The leadership makes the plans and guides the group into working overtime, winning the war, curing the disease, staying together, treating each other according to norms that symbolize respect, and all those forms of investment that, for a strong society, comprise moral positives. Such is the genesis of culture that so exquisitely molds our minds into who we are, identity shaped by the backlog of thought built into language and social norms. There's nothing beyond understanding about its genesis, only a lack of imagination as to the beautiful complexity simple principles can create.
Our lives are filled with opportunity costs, forethought, imagination. We listen to the rumor mill because we need valuable information and we need people to think of us as having valuable information, and we work for others because reciprocity has built everything we enjoy. We love and hate because we value others, and we need to have value in their eyes; these relations create drives that are core to our identity. We collect favors and remember failures. We create art to affect the perspectives of others and create understanding, and this only becomes more amazing when you realize that all language use, construction, and the physical play-acting of our social roles constitutes a form of art. All of this is investment.
You didn't think that there was actually some dividing line between offense and defense, action and reaction, empowerment and adaptation, did you? Power is the most obvious form of adaptation. The greatest defense from reality is an god-like offense, and absolute power constitutes absolute control, which constitutes the most effective possible form of security. Denying this just shows a willful misunderstanding of the word "security", which is anything but static and brittle. Predictability makes one vulnerable, and security requires action; given the perpetual imperfection of control, security becomes an art form, too, taking risks at one point to reduce them later, responding and keeping options open, calculating and recalculating, a sort of dancing with your environment. There's a reason they call it "martial arts".
Absolute power is absolutely impossible, but the empowered perspective is the one that makes sense. Investment over time for the sake of power works, and seeking the greatest possible level of control is, beyond the dictates of our subjective interpretations of the world, truly rational. Nietzsche understood this, and it guided his perspective throughout his productive period. The will to survive and the will to power are the same, and other bases of thought are riffs on flawed interpretations.