Musk is playing the numbers. Maximum bang for the buck is from reducing consumption at the high end.
If you make a freight truck 60,000lb, 5 miles/gallon get 6 miles a gallon thats a huge win. because over 30 mile, you save one gallon. If you make a small car get 35 mile/gallon instead of 30, you need to drive 200+ mile to save that gallon.
Consider now total miles driven by big and small, and it gets interesting quick. Freight trucks stay on the road a lot longer than Joe Blow goin to work.
But for SUV vs tiny car, similar numbers apply, even absent the discrepancy in total miles driven. SUV man drives about the same as small car man. First make the big ones more efficient. Saving the big gas hogs a lot of money may chafe, but also the quickest way to their black little hearts is thru their wallets.
or you could establish a dictatorship, decree small cars for only those that need them, massive public transit infrastructure and unicorns in the USA. Or await a political revolution, or work to create one. Musk is doing what he can, given what he sees. Others see things differently.
sidd