By way of introduction, he said that when he was younger he had worked for a construction company.
In this sentence, I would like to know why past perfect tense is used for "he had worked".
Is it because of "he said"? I learned past perfect tense is used for marking two events are related, and the previous event uses the past perfect tense.
But in this sentence, I am not sure why it is used. Could you please help me? Thank you.