I think Mob informant Vinnie Teresa is the one who claimed that Galante bombed Costello's mausoleum. Don't think anything was ever proved. Teresa said that Galante hated Costello but never really explained why. He didn't like Gambino either, for that matter. Because Galante was a big Bonanno defender, it would seem more logical that he would have hated Steve Magaddino or Joe Colombo, since they had more to do with deposing his old boss than anyone else.