We exist in a social system and culture that teaches us that the way to survive, and "get ahead" materially, is to compete for positions of power, gain dominance over others, and, ultimately, become an owner of productive property and exploit others. Not surprisingly, many people come to greedily and competitively crave power and wealth above all else.
But such behaviour is not a fixture of human nature. People clearly have the capability of being cooperative as well as competitive, supportive and helpful as well as antagonistic, egalitarian as well as selfish. All of these qualities are part of "human nature." We can and do choose to employ one quality or the other, depending on how our material circumstances and interests affect us, and how we perceive our own self-interest. It is also part of our human nature to think, evaluate our circumstances and change our behaviour when we conclude that doing so is in our self-interest. The real problem is the capitalist mode of production and distribution, and the ideologies that have been conjured to defend it and to keep us blind to its problems.