It's a real mixture of trying to decide who these people actually are and how capable they actually were.
Firstly, yes they are all coming across as gormless idiots, but obviously they are playing a role here in an absolute hard nosed attempt of not saying anything of note that can actually incriminate themselves leading to a future prosecution.
This is giving the impression that they hadn't a clue what they were doing.
But there is just too much evidence that suggests that they did know what they were doing. And what they were doing was actively ignoring, playing down and wilfully avoiding any evidence presented to them that the Horizon system was not in fact robust and that there were serious bugs in the system.
It's almost as though because they believed that some people at the sharp end historically had in fact had their "fingers in the till" all Horizon was doing was proving this. Plus the fact that in relation to the numbers using the system on a daily basis who were not reporting issues, it almost allowed them to take the majority view and ignore the minority experiencing issues.
Then the major issues around negative media, separation of the two identities, floatation, not wanting to "open a can of worms" etc etc. It was a huge boiling point of denial actively played out by a board and exec who seemed to encourage each other to continue down the route of denial rather than question whether there really was merit in the fact Horizon was unsafe.
Some simply didn't believe there was anything wrong with the system so why bother investigating something they believed to be working well. Where as others had different views.