Causation is not established by that chart, I suspect some of the decline was due to piracy, but with no evidence it seems like it could be attributed to other

Causation is not established by that chart, I suspect some of the decline was due to piracy, but with no evidence it seems like it could be attributed to other factors. For example there's a drop in vinyl in the late 70's on the chart, at which time napster wasn't a thing.