There was a pollen grain analysis study published a few years back that indicated a broad regional climatic shift, drought, and subsequent widespread famine resulted in mass migration. There are also cuneiform tablet correspondences between Near Eastern empires and Egypt in that time period attesting grain shortages and general civil unrest. So it's less likely that it was a disruption in tin trade directly that ended the LBA and more a breakdown and collapse of trade networks when hungry, angry people abandoned cities and went looking for "greener pastures".

This is a very general summary and it's actual way more complex than just sea people are climate refuges but I'd happy to talk more in-depth.