I'm a bit older, white, and grew up in/around plenty of DV - I think it was just more common back then overall - and my understanding of the forgiveness is that it was almost always driven by economics. The man was the provider, the woman was economically trapped, so she forgave and withstood it. If the women had their own income, they'd have left. The other major factor I picked up on was the kids and withstanding it in order to keep the family unit together.
It was never a lack of intelligence or that they actually condoned it. They had to mentally justify it and rationalize it to others. They'd try to avoid it and 'not make him mad' but when it happened again, they rarely ever made the tough choice to leave.