Among the Ten Commandments is the prohibition of idol worship. Rabbi Soloveitchik says there is a close connection between idolatry and adultery. Both represent a kind of betrayal. One is a betrayal against a spouse. The other is a betrayal against Hashem.
Both situations are difficult to comprehend. The transgressor certainly is not taking into account the consequences of his actions.
Such behavior is a serious renouncement of the purity of the relationship that individual had with his spouse or G-d. He has reached a point of no return. It is a severance of a once holy relationship.
The road back is long and difficult. If the woman committed adultery, there is no returning. If people would only think before acting, so much unnecessary grief, could be avoided.