Not (even hardly) proven.
It will be.
There is zero path to airworthiness certification with a known single point of failure, period.
To get to a point of certification without criminality you have to believe that the entirety of the engineering team at BOEING, all of them, from top to bottom were utterly incompetent and that everyone in the FAA involved in the certification process was also incompetent to an impossible degree.
There is no doubt whatsoever that criminality was involved in the certification of this plane. It’s not a matter of if it will be proven, only when.