You need a seriously screwed-up culture in the detention facility for this to even be considered by guards, much less attempted. Why would anyone assume that only the two guards that were indicted are somehow the only bad apples there and that everyone else is great at their job?
It would be interesting to compare the guards at this facility with others on topics like complaints from detainees or disciplinary actions, to get a better idea of how unusual this behavior was. So far 100% of the COs involved have demonstrated to be highly incompetent and even dishonest.
I have no particular opinion about what exactly happened to cause his death (mainly because I don't pass judgment based on the little evidence I have) but it's easy to see why many would consider these actions proof of a conspiracy though.