Oliver Cromwell was a part of the gentry: neither a peasant, nor a royal--just middle class. He subscribed to the values of the middle class and fought for them, above all for equality, the making-the-same of all people that continues today. At one point, he lost his land, and it is a question what effect that loss had on his demand for equality; from a psychological perspective, it must have intensified it.
It wasn't simply a matter of politics for him. As a Puritan, he believed in the Doctrine of Total Depravity, according to which man is so totally depraved that he is simply incapable of choosing good; on the contrary, he thought, man can not choose good, but--god has to predestine man to salvation. So when Oliver Cromwell looked at King Charles, he saw someone who thinks he is better than the rest, someone who thinks himself above others.
Actually, King Charles did think that, and so did the royalty and nobility. What did the richest and most powerful of England have in common with stinking peasants with bad teeth who had a tendency to lie all the time? All they were good for were their pretty young virgins, and the droit du seigneur, the right of the lord to sleep with a virgin on her wedding night, guaranteed them that. As for the virgins and their husbands, what were they going to do, call the police? Some say this Right of the First Night is a historical myth; I say calling it a historical myth is the upper class trying to re-write its most egregious and direct uses of power out of history, because that historical fact certainly has the power to induce resentment against the rich and powerful even today.
Oliver Cromwell, the Protestant soldiers of the New Model Army, who'd sing hymns before battle, and the Parliament, the political counterweight to the King's will, all saw this and the thousand and one other uses and abuses of the middle-class that the upper class made, and it made them resentful; for their part, King Charles, the royalty, and the Catholic Church looked at them as the ignorant rabble, uneducated, incapable of interpreting the bible, prone to hallucination, and altogether like children.
They were both right, but Cromwell had more might.
Cromwell killed Charles I and neutered his son, Charles II, and he set up a "just" government. He wiped out scores of Irish Catholics (do we call it a "genocide," or was it just a "massacre"?), and they closed down The Globe. Shakespeare was a bad influence on the people, you see. Verily I say unto you that, looking back, we can see whence Ayatollah Khomeini got his inspiration. No dancing, no drinking, no painting, no having fun; just Jesus. Although, to be fair, and balanced, you can do anything that you want in Iran today, just as long as the mollah gets his pay.
The same ideology that was born between the Protestant and Catholic wars in 17th century England is the same ideology that conquered the United States.
It's very simple. The people who got on boats and came to America were the very same Calvinists. Their ideology is the dominant one in the United States of America. It is true that people came to the US from different countries, but their minds were taken over. All of them. Even the Mexicans today are being converted to Protestantism. Mexican Protestants...
That's whom you're dealing with my taxi-driver friend: Oliver Cromwell Protestants.