Cannibal Holocaust

In 1979, an American film crew disappears in the Amazon rainforest while on an expedition to film a documentary about indigenous cannibal tribes. The team consists of Alan Yates, the director; Faye Daniels, his girlfriend and script girl; and two cameramen, Jack Anders and Mark Tomaso. Harold Monroe, an anthropologist at New York University, agrees to lead a rescue team in hopes of finding the missing filmmakers alive. In anticipation of his arrival, the military conducts a raid on a local tribe known as the Yacumo and takes a young Yacumo male hostage in order to help negotiate with the natives. Monroe flies in via floatplane and is introduced to his guides, Chaco and his assistant, Miguel.
After several days of trekking through the jungle, the group encounters the Yacumo tribe. They arrange the release of their hostage in exchange for being taken to the Yacumo village. Once there, the group initially meets hostility and learns that the film team had caused great unrest among the people. The next day, Monroe and his guides head deeper into the rainforest to locate two warring cannibal tribes, the YaÌ§nomamÃ¶ and the Shamatari. They encounter a group of Shamatari warriors and follow them to a riverbank where they save a smaller group of YaÌ§nomamÃ¶ from certain death. Grateful, the YaÌ§nomamÃ¶ invite Monroe and his team back to their village, yet they treat the outsiders with suspicion. To gain their trust, Monroe bathes naked in a river. A group of friendly YaÌ§nomamÃ¶ women emerge to join him and playfully bathe with him. After, they take him to a shrine where he discovers the rotting remains of the missing American filmmakers. Upset and angered, Monroe decides it is of utmost importance to recover the films. He confronts the YaÌ§nomamÃ¶, during which time he plays a tape recorder of tribal music for them. The intrigued natives agree to trade it for the first team's surviving reels of film during a cannibalistic ceremony, in which Monroe has to take part.
Back in New York, executives of the Pan American Broadcasting System invite Monroe to host a broadcast of the documentary to be made from the recovered film. Monroe insists on viewing the raw footage first. The executives first introduce him to Alan's work by showing an excerpt from his previous documentary, The Last Road to Hell. One of the executives tells Monroe that Alan staged the scene to get more exciting footage. Monroe then views the recovered footage, which first follows the group's trek through the jungle. After walking for days, their guide, Felipe, is bitten by a venomous snake. The group amputates Felipe's leg with a machete in an attempt to save his life, but he quickly dies and is left behind. The remaining four succeed in locating the Yacumo. Jack shoots one in the leg so they can easily follow him to the village. Once they arrive, the film crew forces the entire tribe into a hut and burn it down in order to stage a massacre for their film. Monroe expresses concern over the staged scenes and poor treatment of the natives, but his worries are ignored.
Monroe finishes viewing the footage and expresses his disgust to station executives about their decision to air the documentary. To convince them otherwise, he shows the remaining, unedited footage, which only he has seen. The final two reels begin with the team locating a young YaÌ§nomamÃ¶ girl, whom the men film and gang-rape as Faye tries to intervene. Afterward, they encounter the same girl impaled on a wooden pole by a riverbank, where they claim the natives killed her. They move on and are attacked by the YaÌ§nomamÃ¶ in revenge for the girl's rape and death. Jack is hit by a spear, and Alan shoots him so the team can film how the natives mutilate his corpse. As the three surviving team members try to escape the scene, Faye is captured. Alan insists that they try to rescue her. Mark continues to film as she is raped, beaten to death and beheaded. The YaÌ§nomamÃ¶ immediately locate the last two team members as the footage ends with Alan's bloody face. Disturbed by what they have seen, the executives order the footage to be destroyed. As Monroe leaves the station, he ponders to himself, wondering "who the real cannibals are."

Question: Why did the American film crew travel to Amazon rainforest?
Answer: To film a documentary about indigenous cannibal tribes.