As I recall, both Drews and Cline go into this theory in more detail and dismiss it.
There could be additional contributing causes of course.
Missing evidence of iron weapons among the sea people is more of a concern. But we still don't know why people became "sea people", but as I understand it a common theory is that it was due to an economic collapse which had already happened. So, the hypothesis is that the economic collapse could be (at least partly) related to the emergence of iron and its impact on the bronze cartels. Whatever the cause, the bronze age collapse as well as the origin of the sea people is very interesting.
My intuition on the "Sea People" issue is that there was both push and pull. A people change their way of life when the old way becomes less attractive (the push) and a new way becomes more attractive (the pull). The first effect could be due to environmental conditions and failure of trade, the second could be due to exposed vulnerability of the existing order of things to exploitation (the Drews theory). Positive feedback could occur on both.
what prevents bronze from being "worked nearly everywhere by nearly everyone" or to put it another way what make iron easier to work?
If you had asked me I would have said the opposite. bronze is nice and easy to work while iron requires much hotter fires and harder implements.
But yeah, one can just cast bronze much more easily than one can cast iron. The melting point of bronze is about 200 to 300 C lower (and 500 C lower than cast steel.)