This possibility is based on a few things

#1 To say that it was difficult for the early Saints to practice polygamy is an understatement–particularly because of their religious heritage and social context. They knew that they would never again be seen as honorable and decent people by the rest of the world.

#2 These early Saints had seen Joseph bring forth the Book of Mormon, they had witnessed miracles and stunning doctrine come forth from him. They had no doubt that he was a prophet.

#3 While the Saints were dedicated to Brigham, the introduction of polygamy after Joseph’s death may have led many to doubt. There were several splinter groups at the time, and the introduction may have made the claims of the RLDS Church much more convincing.

#4 Because Joseph had practiced polygamy, there was no room for saying that the practice was evidence that Brigham Young was a false prophet who just wanted to expand his sexual opportunities.