What a bunch of unfounded, uninformative verbosity. The whole presentation is based on, without underlying proof, the old Documentary Hypothesis. This theory basically assumes, with zero evidence, that the Pentateuch and historical books of the Old Testament could not possibly have been written before Israel's return from exile (538 BC and following). Early versions of this claimed that writing had not been invented at the (estimated) time of Moses, which is ludicrous. One basic foundation of the theory is that different writing styles prove that the Pentateuch had to have been written by multiple writers and then mashed together. As if individual authors do not vary in style when writing about different topics and purposes. E.G. my writing style certainly is different when writing about news and politics here in TBR than my style when I write about voltage mode and current mode switchmode power supplies or the difference between pulse width modulation and phase modulation.
More to the point, this lecturer assumes - sans evidence - that Moses could not possibly have warned Israel about the consequences of obedience and disobedience in Deuteronomy, and then other authors wrote the history of what happened in the following couple of centuries. To this lecturer, Deuteronomy, Joshua, Judges, and 1 and 2 Samuel had to have been written by some author 500-800 years later as some sort of mythic morality tale.
Contrary to the lecturer's claim in the first part of the lecture, the Philistines were not a Canaanite people, but apparently were from the Aegean area, possibly the areas of Greece, Crete, or the coast of Asia Minor. Their culture was distinctive, including the gods they worshiped. They came to what came to be called Philistia around the time of the 12th Century Bronze Age collapse (when the Minoan culture on Crete, the Mycenaean culture on Greece, and the Hittite empire in Asia Minor collapsed).