Why was George Washington called the precedent president?

Washington was the first President of the United States under the US Constitution.

Everything he did set a precedent. Moreover, he was very highly respected as a founding father of the new republic, so the precedents that he set carried a great deal of weight. Another factor was that the idea of electing a president was new and the US Constitution became a model for many other later constitutional governments. Washington and the US presidency thus became a model for presidents of other countries.