Firstly the Rishonim didn’t write nearly as extensively on the Yerushalmi
Secondly being that the Bavli was written later , halacha K’basrah, we always pasken with the Bavli over the Yerushalmi. Therefore if you are looking to learn a sugya aliva d’hichasa it has to be done based on the Bavli. The Rambam, Shulcha Orech etc are primarily based on Talmid Bavli.
Therefore there is a much greater focus on it.