It wouldn't shock me if some donors are still supportive for other reasons. I don't want to get into someone else's head but this was a financial decision they made, however large or small. A lot of people don't want to be told they screwed up in that area, or they weren't as careful as they claim they were. It can be wrapped up in their sense of themselves as mature, prudent, and competent individuals. If they admit they screwed up, it messes with some of their worldview.
I'm just spitballing here of course - it is far from my area of expertise. But I think a lot of folks just don't want to admit they messed something up.