Why didn't God lead Israel by the shorter road through the land of the Philistines?

Answer: They might face war and turn back

God said, "If the people face war, they might change their minds and return to Egypt," so He led them by the wilderness road.

“When Pharaoh let the people go, God did not lead them along the road through the land of the Philistines, though it was shorter. For God said, “If the people face war, they might change their minds and return to Egypt.””— Exodus 13:17 (BSB)