Taking each transmission on its own merit, what would likely have had to occur to trigger the first automatic ACARS alert. ...
I totally agree - reverse engineering a fault tree would be one of the few reasonable approaches to speculating about what has actually happened as opposed to seeing whether circumstances fit a particular external event...
So, if I recall correctly a/p disengage and alternate law are claimed to be the first messages, so using occam's razor, what could have triggered that?
On a parallel note, PRIM/SEC 1 are on the same DC bus, right?