I read this and another half-dozen replies to the parent comment (but not the article, of course...) and was still confused. This comment was the clearest to getting me to understand it.

Example contributors as I presently understand it:

- we transport fossil fuels further around world (i.e. Middle East to the US)

- we transport most other goods some shorter distances

- iron ore transport is "up there" with fossil fuels; high ton-miles of transport.

And of course the cost of transport for a good is a function of distance, a la the rocket equation mentioned in other comments.

And the article is focused on making this point in the context of the effect of reduced demand for fossil fuels and steel (iron ore) on maritime demand. (which is interesting, and totally not what the article title was leading my brain to think about)

Edit: And then I went and actually looked at the figure at the top of the article; guess the real topic is yet a different framing than what I comment on above!