I think you have to look at causation in the legal sense. In English law causation is a question of a "but for" test. Basically would the disatster have taken place if all of these fuck ups hadn't happened
The state and it's institutions had a duty of care, they fundamentally failed in that duty (stadium not fit for purpose, lack of preparation, no security certificate, opening the gate etc).
Personally I think causation is a no brainer, if the FA, police, Sheffield council and Sheffield Wednesday had done their jobs even moderately well, it wouldn't have happened.