Hijacking of the mankind's agenda by powerful groups

What has always interested me is why humans behave the way they do in political economic and cultural matters-in a way which seems to move away from the supposed goals of mankind as a whole. For instance ,our intention should be to achieve progress in the welfare of mankind through a planned effort at achieving peace and prosperity for the humankind as a whole but somewhere along the way a few powerful vested interests come on the scene and hijack the agenda away from these goals and manage to put the world on the path to war and destruction(e.g.Iraq,Bosnia etc.) .Likewise when we are trying to achieve sanity in beliefs and faiths,there comes along a group of people who espouse narrow causes ,fundamentalism and ideological dogma. Culturally just when our art and culture has reached its pinnacle of glory there come movements towards anti-art and away from the blossoming of human talent, towards kitsch and deliberate uglification.