It’s first of all a heads can roll kind of thing where jobs can be at stake even for just negligence.
Secondly, I guess I’ve heard too many they “murdered him” or they “wanted him to die” claims.
Thirdly, they know that this is the first thing that will be claimed and it is a huge task disproving beliefs even with facts.
Finally, I work with a fair amount of prison officials and just don’t find that they would willfully allow him to kill himself to cover up evidence.