Didn't read the study so forgive me if this has already been addressed in it, but I imagine the fact that prior generations of blacks not being able to pass on estates (i.e. unable to legally own title to property due to Jim Crow/Reconstruction ancestors) plays a huge part in this. For example, my father inherited a little bit of wealth from his parents via property and assets, helping get us through a difficult financial stretch in my childhood. His parents inherited a nice sum themselves during the Depression, enabling them to eventually pass on those assets to my father.
Overall, this generational wealth will be almost invaluable to millennials like myself. While I could survive well without it, I will certainly now be able to pass on substantially more wealth to my son, ultimately because greatparents were successful enough (and fortunate enough) not to be racially discriminated against. From the perspective of an African American, I find this generational wealth to be an immense privilege, something I cannot and have not taken lightly or for granted. In many ways, my great fortune was winning the genetic lottery, in the sense that I was lucky enough not to be discriminated against as a Caucasian.