A very calculated guy who is not an emo who’s a jerk as much as people larp it, He is a genius even in his own part and not just punch first think later, but he is actually analyze first then punch after
12:17 That's absolutely Darby younger's fault. Not having the foresight to look out for trickery, especially when he should absolutely know of Joseph's ability. He got too confident because he thought he could read all of them that it led to his downfall. Jotaro observed and took advantage of his confidence by playing into it
I feel the one thing about this that causes most people to write it off is that half the Jojo's think this way anyways and somewhat cheapens the impact when Jotaro's deductive skills are a main point of his. Bruno: If we go outside, there's no telling what the effects of the stand might do to- Giorno (also a purposeful biologist): Ice cubes. Bruno: ICE CUBES!? Pesci: Ice cubes.
11:22 specifically he had d'arby question if jotaro could stop time just like Dio, even if jotaro didn't know it at the time. D'arby knew Dio's stand abilities and when he saw jotaro, he saw a stand that moved very similarly to the world. Given that and dio's relation to the joestars, he had to consider even the tiniest possibility that jotaro could stop time as well, and if he could, then he can switch all 5 cards.
I think the reason why Jotaro is so skilled at observing things because he has absolutely 0 self doubt and, most importantly, he NEVER assigns ANY Detail as "ah, must have been nothing". That is, at least in my humble opinion, the biggest lesson to be learnt from him as a character. "It's never nothing" so to speak.
I'm glad you've brought light to Jotaro's deductive abilities because WOW that man is brilliant Like, he is genuinely a genius-level detective that has some insane powers of observation and reason, yet it is NEVER brought up by anyone else Jotaro often get's downplayed as being a creative stander because Star Platinum's stats, but somehow they also fail to realize that his stats don't always save him - in fact, they're often countered - it's his strategic and analytical mind that does. Honestly, while he's not like Sherlock Holmes-level of genius anime characters, I still think that he is a force to be reconned with even by characters like them because he is close enough to them to play their games.
Wasn't one of star platinums strengths back in part 3 (like that was highlighted) his insane precision? I'm pretty sure jotaros keen observation is linked to that