[altacc]

Applying Occam's razor, an unusual event like sabotage would need more than circumstantial evidence. There is a long list of contributing factors towards corporate negligence that makes an accident much more likely.

One thing that hasn't been mentioned in this thread yet is that the training for workers at the time of the accident was a small fraction of that originally intended for workers at the plant, and the reason for this was a financial decision taken by plant management under pressure from Union Carbide, not because the training wasn't needed.

A probable cause of the incident was water left in pipes by a worker, ordered by a novice supervisor, washing out a pipe; a process that was prohibited by plant rules. Extensive and repeated training imprints processes & rules into people's minds. If that action was the cause then with better training, both worker and supervisor would have known not to do this.