That choice is w-a-a-a-y down on my list of reasons.
That's not how 0bama typically chooses people to work for him.
No, competence rarely enters into the equation, even liberal competence. But it’s not impossible that he chose someone competant in a position like this, heading OMB isn’t really a policy making position. An intelligent ideologue would have put competent people in non-policy making administrative positions starting day one. You need a competent bus driver to stay on the road while you throw people under it. Don’t rule out the possibility that he’s learning on the job, or be fooled by it.