en_tn/1sa/15/17.md

were you not made the head of the tribes of Israel?

Saul knows that God made him king, this question is used for emphasis. (See: rc://en/ta/man/translate/figs-rquestion)

Why then did you not obey the voice of Yahweh, but instead you seized the booty and did what was evil in the sight of Yahweh?

This questions is asked to rebuke Saul for disobeying Yahweh.

but instead you seized the booty

The Law of Moses specifically states when God instructs Israel to completely destroy a nation, nothing is to be kept. It is all marked for destruction as a burnt offering to God. Nothing was to be kept or brought back to camp.