I don't know that I agree with that. Not trying to be needlessly argumentative, but I will add my impressions.
First of all, the under-slab drains never appeared to me to work properly. They were constantly charged with water and when the spillway was in use, they jetted water, something that an under-slab drainage system is never designed to do at the pressures displayed by prior photos.
The drains were the primary cause of failure in my opinion, due to their shallow placement thinning the slab. They built in the failure at an early point in the service life of a slab that might have lasted 300 years instead of 50.
To me, the causes of this were (1) Design of both spillways, (2) Detailing Errors and lack of Supervision, (3) Unauthorized Field Adaptation of Construction Details, and (4) Poor Owner Supervision, QC and Follow-up Maintenance of the Construction and Subsequent Operation.
I don’t totally disagree with your causes, but I might reverse the order of precedence. Had the drains been properly maintained, this failure wouldn’t have happened. The water from the non-working drains was going SOMEWHERE, it didn’t just evaporate. When they quit working, that should have been a huge red flag to the operators.
I think that water was busy washing out the soil and rocks from beneath the slab, finally to such a point that it failed, either from uplift, or lack of support from the subgrade.
Sure, the additional cracks contributed, as that was just another place for water to infiltrate into the subgrade. At some point there would be more infiltration than the drains could handle, especially if some weren’t working. Also, the cracks contributed to an overall weakening of the slab.
I will posit another theory. The operators (DWR) and the investigators already know this. They knew within an hour of the failure why it happened.
What’s now transpiring is some sort of smoke and mirror exercise that will try and convince everyone that it happened because of ‘normal wear and tear’ or some such.
Baloney, I say. They should have fixed those drains immediately after they quit working, and should have inspected carefully for evidence of washout beneath the slab.
The operators were, and are, negligent.