In the English Civil War of the 1600's, the rebel against the monarchy, who were radical Protestants won for a while. They ran the government. There was no king but a Protector.

But they couldn't govern over time. They disagreed with each other too much about religion and about how government should be. They just couldn't settle down and deliver that frequently dull thing that good government often is.

So some people called back the son of the beheaded king and everyone pretty much went along with it because at some point people in general are tired of intense arguments about government and God and just want to get on with their lives while those who want to do government do it without bothering other people much.