Upen's decision was absolutely partial but I don't think it was stupid.
Karishma was the first one to do the task and hence no one knows what the game was.
When Punit did the task, Karishma knows about it. Punit was angry over the fact that she denied to do the task bcoz she knows the cause.
When it was time for Sushant, no one was ready to help him. In case of Karishma and Punit, ppl did help them without knowing the fact. But when they got to know, they were not ready to help sushant.
So he decided to suggest Sushant's name for appreciation.
Personally he was offended by Gautam and they asked to name a person to be punished. Since, they didn't ask him to discuss with the team and conclude, he took his hatred towards Gautam.
He was partial but not a stupid to let go of the chance which he gets. Since he was calm, ppl digged at him and now he is no more fool to let go of everything and be a sage.
P.S: Not a Upen fan