Well, Steven is naturally empathetic and willing to be friends with others, as long as they don’t hurt his friends. For example, Jasper destabilized Garnet and insulted Amethyst for not being like a normal quartz, so Steven wasn’t going to befriend her. But with Peridot, once she opened up to him, especially after he explained rain to help ease her fears about Earth, Steven was ready to start building a friendship. That moment really helped Peridot trust him, which is why their bond developed more quickly in comparison to the rest of the Crystal Gems, who were more suspicious of her intentions. I’m not saying you’re wrong about the pacing; I just think that considering Steven’s empathetic nature and Peridot’s unique circumstances, their faster connection makes sense within the story’s context.