Tbf if we weren’t shipping that stuff with one big ship it would be like 2000 planes.
I’m not saying there aren’t ways to improve cargo ships, like trying to build ones that are “greener”, or simply trying to reduce how much stuff we ship overseas.
But that’s the difficult thing in trying to point out “one thing to kill to have the biggest impact”. It’s complicated.
One bus pollutes a lot more than one car, but 100 fewer cars are on the road because of that bus, the bus is “greener” overall.