ACP Pradyumn said sorry because he should've known better than to believe that Dr. Salunkhe will betray his country, his profession, CID and his oldest friend Pradyumn.
I mean he did say his heart never agreed with the narrative that Dr. Salunkhe is a traitor and spy of eye gang. But he did eff all about it ! Did he do atleast an internal investigation to double check the truth as it was presented ? No! Abhijeet ko 10 minute mein samjh aa gaya ye Dr. Salunkhe nehi hai ! He needed another 15 minutes to trick the interloper to reveal the truth himself. If Pradyumn Sir even had kept a wide margin of doubt , Dr. Salunkhe could've been found much earlier . He spent three months in a small cage ,frail and tortured with drugs like an animal.
Pradyumn visited the fake Salunkhe many times yet he couldn't find the truth because he didn't really try. It's one of the flaws of this otherwise nearly perfect and legendary cop and leader , he always easily believes the worst of his compatriots. He suspended Daya over a ridiculous charge . He should have known better ! Daya can die for his country and duty , never betray it.
When that SOS fella came with a similar ridiculous charge, instead of trusting Daya and wait for the truth to come out, he said he'll shoot Daya with his own hand if he turned out to be a traitor!
Koi bhi random aira gaira raha chalta bhula bhatka chai wale pe aikeen kar lega against his own comrades who've worked with him for decades showing over and over again what they're made of !
He should apologize to Daya as well.
Like I mentioned the writing in this season feels too off
Sure ACP sir suspected his officers even in season 1 but he equally gives them the benifit of doubt as well with Daya case of the dishonest cop and with Abhijeet for whom.he requsted KD to represent him in court
He's the leader of the team , if he tries to help his officers directly he'll be called biased plus during SOS track he was being pressured by both DIG and SOS so he didn't have a choice