If in fact being listed in credits is that important, why wasn’t it in their contract?

Maybe because of the usual power imbalance between employer and employee? If there are enough other applicants, employers can dictate the terms. It‘s a bit like saying to a coal miner: “Oh, if not dying from black lung disease is sooo important to you, why wasn‘t that in your contract?”

“I see a lot of white knighting”

I hate this term. If you call people who care about injustices “white knights”, what do you call the people who go out of their way to defend injustices and take the side of the more powerful parties?