Rav Yakov Kaminetsky - Sotah an explanation -

Emes LYakov (Bamidbar 5:15):The reason for this whole procedure is that when a man suspects his wife of  adultery only G- directly assures him that she is innocent, even though this isn't so for any other sin but rather 2 witnesses alone establish the facts, because the husband will not believe them. Because the husband would not believe even a prophet therefore for the sake of shalom bayis G-d allows His name to be erased and it is as if G-d is directly stating she is innocent therefore the foundation of the law of sotah is not to punish the wife but to ensure the husband believes she is innocent which is the basis of Chullin141a Great is the peace between man and wife, for the Torah has permitted the name of the Holy One, blessed be He, which is to be written in all sanctity, to be washed away in the waters of bitterness,