The system was obviously very much not working. Some of the individuals that caused this acted on negligence, some careless ass-covering, some probably maliciously for their own gain.
But there are a few key points that made it essentially impossible for the accused postmasters to defend themselves against the allegations, among them as a key point the presumption that computer records are correct and must be challenged by the defendant, not proven by prosecution. And to challenge these, you’d need to have the internal records that you can’t access as defendant - no surprise that many of the accused entered a plea deal, knowing that they’d never stand a chance in a trial.
Then, the Post office boasting powers to investigate and bring cases, while not being held to the same standards as the Crown Prosecution, meaning no independent review, no challenge.
This basically made all efforts to defend hopeless, and you can see the results. The cases did turn on the outstanding work of a few heroic individuals and a stroke of luck - if not for those, this all would have gone away quietly, with the postmaster convicted, broken, silenced.
A system that allows for that is broken, and the same thing will happen again, unless the shortfalls are addressed, because careless, negligent and even somewhat malicious individuals are plenty, and heroic people defending are rare.
I can recommend reading this, which sheds some light on the legal details that made the scandal possible at this scale. https://emptycity.substack.com/p/how-the-legal-system-made-i...