The servants on the lower decks have their spiritual needs mainly satisfied through religion.
The visiting priests aboard the ship occasionally find their way to the lower levels, spreading the faith in The Emperor through sermons, while exuberantly extolling the great deeds of the Interstellar Warriors as Emperor Angels.
And these tales are naturally the most alluring to the youth.
The admiration for the Interstellar Warriors is quite strong among the people.
It's not just Rex; most of the recruited youths, upon learning that they have a chance to become a Phoenix recruit this time, are extremely excited and hopeful.
Russell is quite pleased with the youths' mental attitude. However, what disappoints him is their physical condition.
Malnutrition, being involved in heavy ship maintenance tasks from their early teens, lacks education, lacks specialized training... The conditions of these youths clearly do not meet the usual recruitment standards of the Interstellar Warriors.