It's a familiar phrase: Power tends to corrupt, and absolute power corrupts absolutely. Great men are almost always bad men.
Katczinsky's character in All Quiet on the Western Front comments about the effects of power on men in the army
"but the root of the matter lies elsewhere. For instance, if you train a dog to eat potatoes and then afterwards put a piece of meat in front of him, he'll snap at it, it's his nature. And if you give a man a little bit of authority he behaves just the same way, he snaps at it too. The things are precisely the same. In himself man is essentially a beast, only he butters it over like a slice of bread with a little decorum. The army is based on that; one man must always have power over the other. The mischief is merely that each one has much too much power."
By why is this generally true?
We like to think that mankind is basically good. But this observation of human nature strikes at the very heart of this notion. If man was basically good then power wouldn't corrupt: it would embellish generosity, provide the means for great benevolence, it would produce love not dread.
Instead I think that man is full of self love. We (I included) crave the adulation of others and that they would do our bidding. We want to be great. So when a person receives power they enjoy it and they wish to prove to themselves that they have it. But how can one do this? By showing that no one can prevent you doing what you want.
So let's pretend that you've been granted absolute power. You begin with reasonable requests. This gives a buzz for a bit – but aren't people just obeying you because what you're asking makes sense? So then come the unreasonable orders – and what a high. People abjectly humiliating themselves to please your every whim. Yes, truly none can prevent your will.
But then the nagging doubts. You can't really do anything, there are moral taboos; don't they represent the rules of some higher power?
Next the subtle whispering begins.
Why should you obey some ancient moral scruples? Who's to say you can't do these things?
Then your conscience fights back screaming – “It's wrong!”
The silky voice replies “Says who? You decide what's right and wrong.”
“God says” your conscience answers.
“Does he really?” scoffs the voice, “Like He'd strike you down?”
“Yes, you'll have to answer,” your conscience musters.
“No you won't. You're the highest power,” the voice encourages. “Now prove it. Violate these superstitions. Show the world you're just like God.”
So that's my theory. When people are given power they need to demonstrate to themselves that they truly have it. The ultimate way to accomplish this is to do something that you know to be morally wrong - even reprehensible – and show that nothing can stop you. To prove that you are answerable to no one. This is our great desire that power unveils: to be like God.
So the fact that power corrupts people is evidence that man is fallen. That the Bible's view of man fits with reality. That we are not naturally good, but rather, selfish, consumed with ourselves and rebels against God. We have all followed after the lie of the serpent in the garden.