You're correct that poor leadership contributed to Union cavalry failures. Union officers generally used their cavalry as more supportive troops than their Confederate counter parts. They were frequently assigned as pickets, guards for officers, and messengers. Whereas men like J.E.B. Stuart and Nathan Bedford Forrest were much more brazen (see Stuart's ride around the Army of the Potomac). The union leadership wasn't all bad; "The Father of U.S. Cavalry" (and Stuart's father-in-law) Philip St. George Cooke helped a lot. But the primary reason was that southern soldiers in the Eastern Theater were better riders than their northern counterparts. This is due to the fact that the South was much more rural than the North. Southerners had to travel farther distance and railroads weren't as much of an option as they were in the North. The CSA had nine thousand miles of railroad compared to the North's twenty thousand. Also, the South already had an organized group of men who were adept riders: slave patrols. While slave patrols in cities, were generally on foot, rural slave patrols would be frequently on horseback. Slave patrols would also provide the foundation of the Klu Klux Klan. So to sum up my point, southern soldiers in the Eastern Theater had more experience horse-riding compared to their northern counterparts. Both belligerents' areas in the West were more rural, so their soldiers would be better at horse-riding. Leadership did contribute to the Union's early failures in the eastern theater, but it was largely difference in cultures. If you require more sources or have any more questions, please let me know.