Another theme in Samuel is the adopted son replacing the natural son. Samuel is ‘adopted’ by Eli. Saul was ‘adopted’ as Samuel’s son. And, David was ‘adopted by Saul.’
Unlike Genesis, it isn’t just the younger son that replaces the older; it’s the adopted son. The principle has been amplified. (How much more in the NT, where Jesus, the miracle-born son of promise, from Galilee is ‘adopted’ — not in the Arian sense?).
Eli’s sons were taking the Lord’s portion of the sacrifice, seizing raw meat from the people, and sleeping with the woman who served in the tabernacle. So, Samuel, the adopted son, came by God’s sovereign hand. Eli’s house was cut off progressively throughout the book (1 Sam. 4:11, 18, 14:3, 22:9-23)
Samuel was not a descendant of Aaron, but actually was a Levite (1 Chron 6:22-30; pg. 49). The priests were not faithful, so God speaks through a prophet.
After the Samuel story, the Israelites lose 4,000 men symbolizing the Philistine attack affected all four sides of the land (1 Sam 4:2). But, the head of Dagon was eventually crushed, like the head wounds of Eli’s house [a theme prominent in Judges too, straight from Genesis 3:15)].
Yet, the Levites who receive the ark after the Philistine defeat do not do favorably. All burnt offerings are supposed to be male, but they sacrificed the cows which brought the ark back?!
The Lord’s “sons” — Eli, his sons, the Levites, all of them keep failing the Lord. That’s why Samuel, the adopted son, was called upon by the Lord’s Spirit.