I don't think he trapped him. They had a nice relationship before becoming FWB. And he was very gentle with him during their first time together and he asked if YeJun wanted to continue or not. If he was truly awful he would have forced him. But now, as an omega, sex should be very smooth. Also, he got mate bonded w/o his consent, so he's pretty pissed. Noah/YeJun ran away and hid pretty well so even if Ian/DoYoon had wanted to find him it would have been very hard. Also, he hadn't associated YeJun w/ being an omega bcz he had no recollection of that rut except for the pheromone scent of that omega so he probably didn't come to that conclusion til later.
Well that could have happened if we think logically but considering the fact that we are reading an omegaverse that too with a beta turning into an omega we can't deny the possibility that he might actually be manipulative. Even if he wasn't directly involved he still looks calculative and not a green flag. I hope I'm wrong tho their kid is too cute and I can't deal with one more tragic storyline ಥ_ಥ
This guy's seems too calculative it's seems like he trapped the mc to begin with and played with him psychologically in the past. It reminds of those plots where the crazy psychotic alphas turn the betas into omegas