The ML says that it was "love at first sight" and just because of that, you don´t have to get married to a complete stranger. ML becomes VERY possesive and obssesive over MC, but they cover it up through saying:
"His mother left him when he was a child and that is why he has separation anxiety." 
That doesn´t let the ML take over MC life. Also, Mc is a bit dumb and just let´s the ML do whatever he wants with him because:
"It´s the first time anyone wants me, so I have to love them back!" type scenario.
ML also gets berserk because of people that says that ML shouldn´t have married Mc because he´s an commoner and a beta. That means no heir, but, ML drugs MC, so that he turns into an omega.

In one of the first chapters MC kills the wife because of rage, and he gets locked up becuase he killed the wife. But ML doesn't care much about it and knocks him out. ML puts him later through 🍇 and other things saying "because you killed him, you should become my wife in his stead".