We've got a decent idea, as you'll see below. More can always be said if anyone would like to contribute to this topic further, please don't let this post stop you! In the meantime, OP, here's some previous posts for your consideration:

• u/Bentresh examines the Collapse as experienced by the Egyptians and the Hittites; and here's also a roundup of their previous posts on the Sea Peoples;
• Still on the Sea Peoples, here's u/kookingpot examining the Philistines;

As regards the so-called 'Collapse', here's a few more relevant posts:

• Here's an AMA with Eric Cline, author of 1177 BC: The Year Civilization Collapsed;
• But there is reason to doubt the 'Collapse' narrative, as u/UndercoverClassicist examines in this post.