> Compare that to ~30% of all energy use for transportation
Transportation, especially ALL transportation, does a LOT. You're looking for ROI not the absolute values. I think it's undeniable that the positive economic effect of every car, truck, train, and plane is unfathomably huge. That's trains moving minerals, planes moving people, trucks transporting goods, and hundreds of combinations thereof, all interconnected. Literally no economic activity would happen without transportation, including the transition to green energy sources, of which would improve the emissions from transportation.
I think it might be more emissions-efficient at generating value than AI by a factor exceeding the 7.5x energy use. Moving rocks from (place with rocks) to (place that needs rocks) continues to be just an insanely good thing for humanity.
Also, I'm not sure about your math. 4% would be 4% of the whole like in a pie chart, not 4% of the remainder after removing one slice. 4% AI, 30% transportation, 66% other. I don't know where that 40% is from.