During an interview with The Town podcast, Marvel Studios producer Nate Moore revealed that studio head Kevin Feige rejected the original storyline for Captain America 3.
Moore stated that the original plot was completely different from the events of the Civil War. He explained that the storyline had centered around Baron Zemo and the Madbomb, a device that causes people to fight themselves. In the original script, the titular character and the Winter Soldier were to put a stop to the dangerous device.
However, Feige was not a fan of the plot, which he felt was not good enough. Moore stated, "[Feige] was like, 'That's not a big enough idea, guys.' And we're like, 'Let us write a draft, we'll prove it to you.' As we're getting done with it… he pulls me into his office and he said, 'You know, I think we should try to do Civil War.' And I was like, 'Kevin, we don't have half the stuff that's in Civil War. We don't have the New Warriors, we don't have… Here's all the reasons why we can't do it'... There were so many things that we didn't have. And he's like, 'Go home, read it, let's talk about it.'."
Moore followed Feige's instructions and read the Marvel Comics Civil War storyline. But, he maintained his stance that it would be incredibly difficult to pull off. Ultimately, Feige gave the team a chance to write a draft of the Baron Zemo and Madbomb storyline. However, the Marvel Studios head wasn't satisfied and he eventually put his foot down on what the team should do.