Moon of asteroid Dinkinesh is weirder than thought

This is very puzzling to me: How can such a small object generate enough gravity to retain a moon orbiting it with such a small radius (see the embedded animation lower down in the article)? The asteroid is only 790 meters in diameter, which is the size of a small hill. I'm no physicist, but maybe someone can whip up some calculations to show how this might be possible at all?