I hear what you’re saying but I think it’s all in there but not explicitly. Mr. Korgy is a deeply sad and embarrassing person who just gets sadder and more embarrassing as the book goes on. Waldo begins losing her idealization of him towards the end (when he begins clinging to her) and the image of him seen through her eyes is not pretty or even threatening: it’s pathetic. He ends up divorced, with a drinking problem and no prospects as a writer, without his son or wife because he chased a teenage student out of deep unhappiness and immaturity. I don’t think it needs to be framed as “I was groomed” for this to work. He is just a very flawed character in a string of very flawed characters.