I have a specific case in mind, and suspect it was a prevailing motive.
During the era that Westerns became popular, the US had already destroyed and relocated many aboriginal Natives.
Natives enthusiastically supported, consulted for, and supplied material culture for, the radio and movie industry. Natives foresaw that this was an effective way to preserve their own cultural identity and heritage. Some even volunteered their services.
The result is, many of the Westerns who made use of these Native resources produced reasonably accurate and compassionate portrayals of Natives.