I read a similar thing, many years before Obama, about the rise of SUVs - that emissions standards were tightened for cars, but not for 'light trucks' and SUVs could dodge the standards by claiming to be light trucks.
So this isn't the first time automakers have responded to tightened emissions standards by selling more products that aren't subject to them.
The article also claimed US vehicle makers had the quiet support of a lot of people in government, because Japanese automakers were kicking their ass at making sedans - but due to market differences and import tariffs [1] the foreign manufacturers weren't as competitive in the truck market. As the rise of bigger and bigger vehicles was bad for emissions but good for US automakers, legislators turned a blind eye to it.