Its not that Aditya didnt love or trust her. IMO... Aditya trusted her... but he is someone who has already been a witness to cheating (parents)... Somewhere within he knws that Pooja wasnt like Zoya... who wud be loyal no matter wht.
Yeah.. ryt... he was wrong in assuming at the first go... but she lied, she was in Masoorie instead of Chennai exhibition, with a man holding hands, n then 100th customer, her paintings in Yash's office, 5 cr investment n the list goes on.
Zoya is naive n their relationship nvr had secrets as shown till now. He used to be away frm home n so he didnt hav to reveal anythng. But Pooja n Adi... thr was something... evrythng wasnt perfect. There were secrets n Adi noticed but chose to ignore.
When Adi saw her dead... there arouse a spark to which evrythng added fuel. He still loves her, is deeply hurt that he cant get answers to his qns... is angry that not only did she cheat... but now she is no more... she has escaped frm all the justifications n answers.
Bepaannah shows completely different stories in a diff way. Adi instantly lost that trust in Pooja whereas Zoya inspite of finding a ring not of her size... tends to believe its for her.
Had Pooja been alive, he wud have questioned but now that she is gone... he is taking the liberty to see thngs his way. Adi's way of accepting facts n thngs is way diff from that of Zoya
P.S. I feel they did cheat their partners... hopefully they do. Coz otherwise Adiya isnt possible much logically... the cvs myt justify their partners' emotional reasons to take this wrong path n fault may be their in their respective relationships too!