Sam Hamm didn’t see anything, Warner Bros on the other hand saw tons of money because they owned all those movies.
People don’t own anything in Hollywood, studios own it. Once a screenwriter gets paid for the last word he wrote (usually during final post production) unless he some how got points on gross he won’t get another dime out of that movie or any sequels. They might have to get the credit but that’s it.
You might not care but everything you’ve ever seen on a movie screen is determined by those accounting and credit rules.
That's where the real piracy is in Hollywood, in the bean counters offices stealing it away from the contractually obligated "producers" of the work (Sam Hamm signed for points of profits on his work and saw nothing as I noted because the pirates cooked the books to show it "earned nothing" even though it was a top drawing film that made back its expenses and was not "null".).
Hollywood wouldn't return to the soundstage to make 3 more films in a franchise if the first really did tank as they said.