What is the origin of Emperor Wendi of Sui Dynasty, so stupid that he was cheated by a lonely woman?

A cruel scum, the Northern Zhou Emperor was so kind to him. People say he looks like the son of heaven. Emperor Wu of the Northern Zhou Dynasty thought it was his old friend and didn't kill him. Then he usurped the throne. He also killed more than 90% of the Yuwen family with thousands of troops. The legend that he was killed by his own son is terrible. Now he feels that he died of illness. This way of dying is too comfortable.