It just makes a lot of sence. They become a commercial bank. Now raising capital. They can easily buy out wamu on bargain prices.. change the name on 1000s of retail banks to lets say GoldMan Sachs and now they get the deposits from the public. Again, I could be wrong!
It'd be dumb to dilute the Goldman Sachs name on the retail scene. Much better to keep the well-known WaMu name within the holding company. You could always say..."WaMu...a Goldman Sachs company" in your advertising/publicity.