Because you're clearly not getting the story properly. The whole story is all about a lack of communication.
"I don't know how can he act like a victim"
- Because he is, he was always fearing for his life because of how ruthless Haein's family is.
"he tried to overstep his wife on work when she clearly is the boss"
- First of all, he's the head of the legal team. He's literally just doing his job but Haein is too hardheaded and wants to join her Trillion club before anything else.
"shows she is cold but actually she always had his back in secret"
- That's the thing. She's not really defending Hyunwoo. You gotta see it in his perspective. He is abused multiple times in front of Haein but Haein shows no care and only defends him behind his back. That's why all he knows is that Haein doesn't care anymore.