The use of "by (verb)-ing" to state a reason

Question

Great good luck sometimes touches a person at least once. It touched me. A book he wrote became a best-seller in 16 countries. I bought a house on the beach. My dream had come true.

These sentences are taken from "Dreams Do Come True" by Jim Bishop.

Someone asked me a question concerning it. The question is as "Why did the boy become rich?" If I answer this question by using "by verb-ing" in the following way, is it acceptable or grammatical ?

Ans: The boy became rich by writing a book which became a best-seller in 16 countries.

Answer 1

Grammatically it's fine, although semantically it could be improved.

When the question is "why", you should be able to start your answer with "because..." In other words, the question is about the reason or the cause, not the manner (of becoming rich).

The use of "by {noun}" or "by {gerund}" explains the how, not the why.

If you wanted to involve the book writing in your answer, you could write/say

The boy became rich because he wrote a book which...

Those a subtle nuances and are often overlooked.

Answer 2

Yes, the construction "by verb-ing" is grammatical. Also, your answer is well written and grammatical too. There are no changes I would recommend.