Why does Timothy go along with Mr. Pennybrook's plan in the story, The Ballad of Timothy Touchett, from the collection, Table For Two?

Timothy's earnest interest in becoming an artist, as well as his love and reverence for his craft, gradually subsides in favor of his fondness for the money that Mr. Pennybrook provides him upon completion of a successful sale of a forged autograph. He gradually begins buying himself fancier meals and living in more lavish apartments, indulging in his ill-begotten earnings with increasingly less strain on his conscience. Ultimately, Timothy surrenders himself entirely to the art of forging, abandoning his interest in writing a novel altogether, before he and Mr. Pennybrook are exposed and prosecuted by a police officer who happens to have an outsized appreciation for Leo Tolstoy.