Just a couple of points in reply to a (very well argued) post, Lookleft.
First, from my perspective, none of what you said justifies pilots throwing other pilots under the bus. There are plenty of others out there willing - some of them paid - to do that. If this tragedy turns out to be caused by the pilot alone, let those others show it to be true.
Secondly, you say:
My point about this accident is the descent profile. Even if the student had the unfortunate situation of a control failure, the descent profile would not make it plummet to the ground at a high power setting.
Do you know, for example, what happens when a throttle cable breaks or disconnects from the carby on a 172 of the model involved in this tragedy?
My point is that your point merely begs the question. You assume that the pilot had control over the engine's power. There are recorded circumstances in which a broken or disconnected throttle cable results in the carbie going to the 'default' wide open throttle. We are talking about a first solo in a 172 only 1,000 AGL and the first few seconds of any fault manifesting itself will almost invariably be overtaken by sensory overload - the HSM. The 'muscle memory' CFMM won't stop an engine that's at WOT because the throttle cable's disconnected or broken. When was the last time a student pilot practised dealing with an engine stuck at full power? (I anticipate that some Monday Morning Quarterback will suggest just pulling the mixture, but we're here talking about the first solo in a 172 at 1,000' AGL.)
In my decades of experience in aircraft maintenance, there have been many occasions on which multiple problems arose from just one random fault (or just one tool left in the wrong place, or just one seat rail not engaged, or just one pair of wires transposed in a plug, or just one air vent that dropped out of the roof, or...). That control cable sawing away at the fuel stub on the Bonanza example could have - if the stub had finally sawn off - resulted in the nose pitching immediately down and the pilot at only 1,000 AGL not being able to do anything about it in time - or even at all depending on what the change in rigging tension may have on the ruddervators - while the engine was still running before the air made it to the EDP.