It is a great movie, but Michael Cimino was a complete nutbar. He fabricated claims about his military service, and his depiction of the Vietnam War is wild fantasy.
https://www.hollywoodreporter.com/mo...wisted-910101/
Cimino’s rampaging ego bankrupted a studio with the debacle of Heaven’s Gate, which slammed the door on the American film auteur movement of the 70s.
https://www.cbr.com/heavens-gate-dis...age-directors/