I read that Maharaj caused financial hardship for Kashiram. Why would he do that to a devoted follower?

This was a profound teaching leela from Maharaj. According to Chapter 0, Kashiram developed pride in his ability to give Dakshina, feeling upset if Maharaj didn't accept it. This pride is an obstacle to spiritual progress. To remove this obstacle, Maharaj started demanding excessive Dakshina, even telling him to borrow money from a grocer. This whole leela was designed to make Kashiram realize that he did not truly have the 'power to give.' Once Kashiram understood this and his pride vanished, his financial condition began to improve.