It’s one thing to be gay and living the gay lifestyle, but totally another thing to be gay and then pretend to be straight and actually marry a woman and profess vows that are a total lie. He should have stayed a bachelor and said, when he was pressured to settle down, that he hasn’t found the right person or he wants to focus on his career.
Most people have a problem with the latter, which is a betrayal. I’m assuming the wife was not aware of his gayness.