Custer obviously underestimated the strength of the Indians because he died there.
History has shown Custer had estimated Indian presence to be fairly close to what it was (1800 warriors or so). Actual Indian strength was greatly inflated after the fact by the public (and the military) because that's the only way they could come to grips with how someone like Custer could be defeated by a group of "savages". Custer's defeat was a defeat in detail. He separated the wings of his regiment as he had at the Washita. The river and the Eastern bluffs inhibited two of these wings from aiding each other (Custer sent Reno over the river to attack the village, while he and his 5 troops remained East of the river). The third wing under Benteen dawdled in their support of either wing. The Indians were able to successfully take on each wing in detail, and prevent Reno & Benteen from coming to Custer's aid until it was too late.
Another significant factor in the defeat was in the quantity of repeating arms (especially Winchesters) in the hands of the Indians. They were able to concentrate great firepower at pivotal points during the battle.
Custer's separating his command under other circumstances may not have been the mistake it became. But geography played a role in making it so.
see where soldiers were when they were killed (or where they were found, the Indians took their dead with them)
The markers aren't an accurate portrayal of body locations. They can be generally used to indicate where bodies were found, but many are misplaced, some of the markers meant for the Reno fight were place on the Custer portion of the battleground. Also, the markers near Deep Coulee are especially misplaced because of how the burial was conducted.
Sorry, Reno not Ried... Despite the locations of the markers as the Indians must have displaced some of them before the Army even got there, and the resulting horror of the death of a possible Presidential candidate, the Army would have certainly covered up some of the truth, although its looks bad enough for Custer despite that fact. Reno did go into the village and fled North to higher ground (my daughter and I have walked the entire battlefield and spent time at the museum and cemetery) due to the resistance initially encountered. Benteen was late to the fight for whatever reason, and the 2 Armies were not much help to Custer after they split up. Custer should have kept his Armies together, and American history of the West would probably be totally different than it is now.