Why is a church marriage irreversible, and a priest or monk can return to the world for the sake of human love?

QUESTION: Priests and nuns wear a wedding ring on their fingers, like people who have entered into a marriage union. Why isn’t their decision to return to the world to marry a human being considered second marriage? And can we say that a person who has returned to the world for the sake of human love “loves God with all his heart,” and allows him to participate in Communion?

Why is the choice of union with God reversible, and the rejection of Him in favor of man is not a sin? Why is this not a violation of the commandment of Jesus: “What God has united, let not man separate”? Or are their rings toy?