I gave a fact; that he was having an affair with an older woman who died shortly after the book was published. You are the one who claims that he was upset about child marriage. When we talk about people making things up, let's remember who is basing their posts in facts, and who is basing them in unrelated conjecture.

Here's my "theory". He was having an affair with a woman, and like all hypocrites, he wanted to feel as though it was something that others were guilty of, too. So, he had a woman who, at the end of her life, is having regrets about their relationship. Lewis is upset that she doesn't like their relationship anymore, and he vilifies her and in his writing says that she's not getting into heaven because she's an adultress.

Do I have any proof? No. Do you? No, also. However, this is based on real events that happened to him, and your idea is just "well, maybe he was into child marriage."