How can he make the decision for himself , when the decision is to be made by aapsi sehmathi? Jas and Aly supported Rahul bcoz he promised Aly the immunity. If Aly/and Jas also don’t support him , then there will be absolutely no sehmathi at all. Talking to Aly is not the problem. It was very much needed. But, what was foolish was, he didn’t even try to convince Aly to support him irrespective of immunity. Instead , he went on a rant about some stupid ethics and principles.. He was so egoistic about it.
Also, all the HM thought that , if there’s no aapsi sehmathi, then BB would ask for bahumathi, like in dance task. That’s why even the losing team members are also discussions about the captain ship. (It was shown in the precap but not in the episode, where , Rubina says she’ll support Ejaz, if he saves Abhi, while pavi is saying why can’t I become the captain)? So, may b all were under the impression that BB is gonna ask for voting, and Rahul was over confident that he has the majority 😆. But, BB saara plans ka popat kardiya.
He needed to strike a deal with Nikki to get her to make him captain. JasAly had already supported his candidature so there was no issue there. He need not have discussed any further with Aly. It should have been purely his call. Its quite evident his game is influenced by Aly which is detrimental to him only. He does very well as an independent entity.

. Aly, anyways was selfish, he wanted immunity from Rahul as a captain, as he’s already nominated. He didn’t even try to convince Aly to negotiate. But the tricky part is, he had to talk to them first bcoz he needs both of their aapsi sehmathi as a team. If Jas and Aly refuse to give their aapsi sehmathi , he would not be in contendership anyway. But still, he could have tested Aly’s friendship by suggesting to him that he may not save Aly but can save himself as a captain.