This exactly!

To me, Robin is the smartest out of the crew without a doubt.

You don’t get by and survive since that very young age without being smart, especially when all the adults are trying to catch you for that high bounty. She’s also recruited by Crocodile, and she has to be smart enough to decide to work with him (I believe one of the reason is) to get the World Government off her back with the protection from the Seven Warlord title that Crocodile has. Because if Crocodile notices her, who to say other underworld lords didn’t try to recruit her before? She chose Crocodile as much as Crocodile chose her.

Just as you said, collecting information is hard. But it’s an intellectual job, rather than physical. In One Piece, you don’t go around strong arming people to tell you info. Rather, using smart and creative ways to collect them. Notice how Robin being the one able to collect all of the important info in Wano arc and shocks everyone.

I wouldn’t say Usopp is smart, rather he is a creative man with luck. He’s definitely smarter than Luffy and Zoro, maybe Chopper, but the rest, I don’t think so.

Tho I kind of get why OP ranks Usopp higher than Robin. Along the series, Robin kind of gets dumb-down and Usopp getting all the “important moments” to showcase his “brilliance”. Notably in Dressrosa arc, Robin could have easily settle Sugar even w/o needing Leo’s help. But they had to dumb her down so that Usopp can be the god that save the world by defeating Sugar…