According to the author of the book, Jeroboam was a strong and brave man who worked really hard. King Solomon noticed this and decided to put him in charge of a big important job.
1 Kings 11:28: And the man Jeroboam [was] a mighty man of valour: and Solomon seeing the young man that he was industrious, he made him ruler over all the charge of the house of Joseph. [was industrious: Heb. did work] [charge: Heb. burden]
This verse emphasizes that a person is justified by works and not by faith only, which may contradict the notion of one being "mighty of valour" primarily due to divine will or favor.
James 2:24: Ye see then how that by works a man is justified, and not by faith only.