Samuel said to Saul, You have done foolishly; you have not kept the commandment of Yahweh your God, which he commanded you: for now would Yahweh have established your kingdom on Israel forever.
So Jonathan was out wiping out the Philistines and Saul was around blowing the trumpet, and taking the glory and announcing that he had smitten the Philistines so that the Israelites heard that Saul had smitten the Philistines with a great slaughter.