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.
There we are in solid agreement.
“The operators were, and are, negligent.”
Bingo. Grossly negligent.