I could imagine if, after a data breach, there was a government-run cyber investigative task force that would come into an organization, and be tasked with investigating and fully understanding the nature of the breach. We already have forensic detectives for other crimes, why not this one?
And if it turns out that the failure occurred due to the company acting negligently, a la (whoopsie all the records were in an open S3 bucket) then humans would be found personally liable.
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But in principle, i also agree with the other causes you list. These are very much what GDPR was aimed at improving. It really is a shame when you look at what GDPR could have accomplished if not for malicious compliance by American tech giants, and shitty enforcement (instigated by American tech giants)
Edit: Thinking more about it, this would probably also be positive for security investigators. If a company is stonewalling you and ignoring a legitimate bug report, you now have the option to escalate this to the insurer. Maybe they could even facilitate bug bounty programs for smaller companies