what happen to Tony Blair why did he resign

Tony Blair resigned as prime minister of Great Britain as many years ago he made a promise to his friend, Gordon Brown that when he had been prime minister for a few years he would step down and let Gordon be prime minister for a while. I think it is disgusting that politics and powerful jobs can be shared out in this way. I didn't want Tony Blair as prime minister and I want Gordon Brown even less. Blair should have allowed Brown to become leader of the Labour party but should have called a general election so that the country could decide who was next prime minister.