Why? Simple: If Obama is for the car companies succeeding, the right-wing media have to be against them. Aggressively. (Although, it's funny that when GM ad dollars were flowing Limbaugh's way he sang a very different tune.)
Instead, he lashed out at the carmaker, and refused to believe that GM's robust sales numbers were accurate. In fact, he denounced them as an "absolute crock." Because GM and Detroit autoworkers are the enemy of conservative media.
Note to Rushbo: Keep digging. When the hole's deep enough, shovel the dirt in on yourself. Put up a "head closed" sign with the date so no one will picnic there and get sick.