In a very real sense, the job of President is to do everything all at once. You don't get to prioritize.

I disagree. You don't get to ignore any of the things that have to be done, of course. And there's tons of stuff that you have to push forward because they're important to your party, or your coalition, or your supporters, or just good policy.

But every President gets to set some of the agenda. They get to decide what to tell their people, and what to tell Congressional leaders, is the issue/program/subject that they most want to get done. What they put at the top of their list.

For Obama, it was health care. Sure, there were plenty of other things he wanted. DREAM Act, ENDA, EFCA, banking reform, climate change legislation, etc. etc. etc. But health care was the top priority. When his team was making schedules, cutting deals, setting agendas, and the like, he made the health care bill the matter that he put his main focus on. Which is why that bill got passed (painfully!) while others did not.