To be fair Casso did go after them. He tortured and killed Hydell. He got the information of who else was involved and planned to go after them. From what I understand Angelo was the one pushing this since Casso openly insulted him and Gotti was in jail at the time. I don’t think Gotti wanted to fuck with Casso honestly considering he tried really hard to smooth everything over and eventually put Angelo on the shelf. As for Casso he still ended up killing Eddie Lino. Gotti was always being followed by the media too so it would have been risky to attempt to kill him. Still doesn’t change the fact that Lino, and Boriello l(two close Gotti allies) were killed with no retaliation