Why did Thomas Jefferson referred to the election of 1800 as the revolution of 1800

Well,

Thomas Jefferson called his election "the Revolution of 1800" because it marked the first time that power in America passed from one party to another.

He promised to govern as he felt the Founders intended, based on decentralized government and trust in the people to make the right decisions for themselves. Basically, the observers have regarded Jefferson's election in 1800 as revolutionary. This may be true in a restrained sense of the word, since the change from Federalist leadership to Republican was entirely legal and bloodless.