Insane!
The lead actor is insane! Not just in this film. i’ve read that the natives wanted to kill him, they hated him so much!
The director, clearly insane, too. Who makes a movie based on a real man who transported a steamship out of water and over a mountain, and then actually recreates that very feat for the film? At least in real life, they took the boat apart first, but the film? No! They literally dragged the whole boat over. Unreal! No CGI here, folks, it’s all real. And madness,
The production had a lot of woes, too. Read about it, lots of fun there. Certainly enough to drive people insane, but Kinski and Herzog made it through okay because they were already insane to begin with and continued to make great films after this.
Compare to Apocalypse Now, which broke Coppola completely. He was never the same director again...