God commanded Saul to destroy all of the Amalekites, the people and their possessions, but Saul and Israel decided that some of the stuff of the Amalekites was worth saving,
“He also took Agag king of the Amalekites alive, and utterly destroyed all the people with the edge of the sword. But Saul and the people spared Agag and the best of the sheep, the oxen, the fatlings, the lambs, and all that was good, and were unwilling to utterly destroy them. But everything despised and worthless, that they utterly destroyed” (1 Samuel 15:8-9).
Could not God have given Saul and Israel plenty of good and desirable things? Yes, the God of Israel could have given them so much that they would not have room enough to contain it all, but as it happened, Saul could not see why all the stuff of the Amalekites should be destroyed, and for that, he paid a price far higher than he ever imagined.
Let us believe that God knows what is He doing.