Hope got into science primarily because he wanted to use whatever he'd learned from studying all sorts of things to save the friends who'd fallen in the first game. This line sums it up pretty well: "I wanted to change history, make things better. Not just bring Lightning back. But Vanille, and Fang... and my mother."

That's canon and my headcanon supplements that because Hope's genuinely fascinated by the workings of things around him, hence studying all sorts of scientific disciplines and excelling at physics and archaeology and probably chem in particular. Give him something he's never seen before, like an ancient artifact, a new piece of tech or whatever and he'd want to wine and dine it and be alone with it for a while. Hence why he became a scientist and not follow in Lightning's footsteps or his dad's (though he surpassed his dad anyway).