There's no doubt in my mind Obama and the Dems were never going to break up the big banks either, BUT the biggest reason Dodd-Frank doesn't have much teeth is because the GOP did all they could to protect the big banks and make Dodd-Frank toothless. If the GOP even cared a little bit about the Middle Class and protecting the MC after 2008 they would have got on-board and helped push through a few basic reforms..
But nope, they kept fighting for the banks, and the Dems really don't want to step on the banks toes either. So we got nothing.