There is a saying that politics is a dirty game of interest which only the fittest is a survival of it.
Indeed and truly, it is because there is no influential politician who hasn't spilled humans blood or hasn't taking advantage of others just for a selfish interests.
The periphery of this unjust is the magnitude that the world will enjoy an everlasting peace of only the political orientation would be reviewed and adjusted.
OP, I don't think that it true that every well known politician has spill blood, I don't believe that narrative, though politicians are know to be corrupt people everywhere in the world it I still want you to know that most of them has not spill blood as perceived by you, do you know that the problem most countries are having today with the political class in godfatherism this has eaten deep mainly in Africa, when a so called godfather is been given a position, he directly reach agreement with his godson and transfers such position to him, note those agreements will not just be mere words, they will be backed up with fetish oaths that tends to go against any of both parties that doesn't keep to their own agreement, so you see it may not be as you think it might be the other way round.
Politic is game of interest and the interest in politics surpass every other aspect of the game as you said and we know that already but you should also know that something done by most politicians in power is because of what their godfather want not what they want, so this thing is some difficult most time to comprehend.