1. It was not supposed to exist. Sherman had ordered it abandoned and the guns removed. His order was ignored. For what purpose can be easily guessed at...somebody was making money off of its existance.
2. The fort was used as a recruiting station for Unionist owned slaves, but the bounty monies owed the slave owners hardly ever made it to ex-slave owners. Once the slave was put into service the officers at Fort Pillow changed their names, making it very hard for the ex-slave owner to prove a link to the new soldiers. Someone else was collecting the bounty ($300 a head).
3. The forts commanders wife was living in Memphis and was given a job by the local Union officials to search Southern women for valuables and contriband who were crossing the lines between Confederate and Union controlled areas. She was found to be stealing monies from these women and keeping it for herself.
The reports of the very bad behavior of the men assigned to Fort Pillow most probably has an amount of truth to it. The reports of widespread stealing and the terrorizing of locals is well known. A local population, that had many Unionist amoungest them, who (no matter what the pollitics) suffered from the effects of the illegal activity from this fort.