Carbon footprint doesn't come in to consideration when money is involved.
FA Cup semis used to be at a neutral venue somewhere between the 2 teams. Look at the European cups last year, yes they are selected in advance but why not have a few grounds shortlisted then selected the nearest, two England clubs playing in Madrid, albeit better than 2 London clubs playing in Baku (which isn't even on the European continent).
You have tennis and F1 flying back and forth, zig zagging across the globe, when they could rearrange the route and reduce the overall impact.