Continuity mistake: Hugh's wounds change from when he cuts open the horse to the ending when he is sitting inside the shack. Specifically, a wound on his right shoulder is there and gone between those two sequences. His back wounds also change considerably.
Continuity mistake: When Bridger refuses payment for staying with Glass in the wilderness, his share of the money makes several mysterious movements on Captain Henry's desk throughout the scene. Although we see Bridger's share being handled only once, it goes from near the edge of the desk where Captain Henry placed it, to the edge of the desk in front of Bridger, to one moving bill in the middle of the desk, to all the money having disappeared from Henry's desk. (01:32:00)
Continuity mistake: If you look closely at Glass' face cut when Fitzgerald is biting his earpiece off, it is not bleeding when it should. In fact, it looks like the blood has been painted on his face.
Continuity mistake: When Glass and Fitzgerald are fighting at the end, watch closely as Fitzgerald pulls the knife out of Glass' knee after stabbing him and you will see the knife is soaked in blood. But it becomes clean seconds later before Glass stabs Fitzgerald in the stomach.
Continuity mistake: At the end of the movie, when Glass is chasing Fitzgerald, at the top of the hill before they both plummet to the edge of the stream, you can easily see the stream current below moving right to left. Then, after the fight scene, when Glass is presumably returning back up the hill to his horse, you can again see the stream, but this time the current is moving left to right - as if the camera was now filming Glass moving up the hill but now on the other side of the stream.
Continuity mistake: The appaloosa horse that he gets after saving the Pawnee girl is being ridden bareback, but when he jumps off it before jumping off the cliff there is a saddle under the Buffalo hide - the stirrup is visible.
Continuity mistake: When Glass goes into the river to escape from the chasers, there is a bandage on his head. He loses it after the waterfall, then somehow the bandage comes back. When he manages to grab some wood to save himself, the bandage has gone again.
Continuity mistake: When he falls into water there is no snow around the river, but 10 seconds later there is some.
Answer: The French were lying to the natives. They had kidnapped the woman and then sold them provisions to help the search for her. They benefited further from the Native Americans killing their rivals.