The Philistines were survivors of the Sea Peoples after they were defeated and driven out Egypt.
They also worshipped the “Fish God” -— DAGON.
Do we know who the Sea People were?
In the olden days, 1973 to be exact, my professor of Ancient Near Eastern History had no problem using the Old Testament as a class textbook. It's not unlike what the Saxon Chronicle are to the study of Middle Ages Britain, i.e. HISTORY. Only the most dedicated, stubborn, and obtuse atheists would be stupid enough to claim otherwise.