I think it's tied to the logistics/shipping industry. No matter where you are in Europe, at least 1/3 of trucks are from Poland (source: number I've made up, just to say that trucks from Poland are everywhere).

Probably mostly Scotch.

I am surprised that cz isn't the top exporter of beer. But I know about the microscopes.

That's my interpretation as well, they sought out a commodity for each country which they are the lead exporter for.

My follow-up question is then: Shouldn't countries be able to appear multiple times in a list of that criteria, if they're a top exporter in multiple industries? Were those secondary industries excluded intentionally, or do they not exist?

I think this is just the top European exporters of a given commodity. Not the top global exporters.

Germany has the biggest sex parties for sure. But they are not so much exported as other people come for them.