Very simply. That flight should never have flown. The CFI was culpable. Technically you may be able to blame the lad, though I as yet am not sure I believe he considered himself to be P1 that day. Morally the CFI should be struggling with his principles, though the fact he sanctioned the flight in the conditions he did, I doubt he is.
Legally the accident happened on the second flight, so legally someone in that aircraft was to blame. Fortunately operations like the FTO involved are few and far between. The place in infamous in the region.
Personally I have never worked at a place that would have let that flight go in one of their aircraft.
LF