Why does stefano show remorse for tony?

stefano did lock him in a dungeon and have andre impersonate him to do the killings to frame roman brady. stefano left tony to die in the quicksand and adnre too. later tony locked stefano up in the dungeon where he was kept for revenge. tony was later kidnapped in 1985 and was held on an island form ore than 2o years so andre could take his place.