The thing I find most interesting about Custer is that during the Civil War his men seemed to love him and would follow him anywhere, but after that war ended, and he went out west, he became widely hated by his troops. At West Point he was a prankster and always skating within a demerit or two of being dismissed, but after the war he became a different person.
You point out something I never really thought of about him.
He was certainly hated by his peers during the war - the rivalry with Merritt and Wilson is noted often. Even Kilpatrick was jealous of him.
He did have a reputation for beating soldiers who were disobedient - with whips.
The more I read about his post war years the more I believe he was probably an egomaniac who needed attention like a drug. Supposedly he was one of the most photographed people in the 19th century.
That kind of attention whoring will create a lot of haters. Add to that his disgust with his rank and not being promoted for 10 years. His poor financial situation and poor investments. He needed another “victory” to propel him into the papers again.
Bringing Mark Kellogg along for the ride was against orders, but he needed the press.