Chunilal did what he did because Bepin Babu did not help him at a time when he had no money and required a job. However, Bepin Babu did not do anything for him. So he wanted to punish him by rekindling haunting memory of his fall near Hudroo.
Chunilal seems to be a good writer with very fertile imagination. That is what he believes would help him to tide over his bad phase.