“Custer had plenty of time to form an opinion on the reliability of Benteen and Reno”
Reno and Benteen were senior commanders with West Point graduation (Reno) and Civil War experience (Reno/Benteen). Benteen had fought the Indians at Washita.
In the military, the “reliability” thing isn’t an excuse. DUTY is what counts. Orders have to be obeyed without question.
Both Benteen and Reno ignored their mission and made a cold betrayal.