mseyfang POSTULATED that perhaps some sort of flutter issue may have led to instant disintigration.
Theoretically possible- but not probable.
Flutter testing is standard in the industry, and FBW can automatically reduce such possibilities. helicopters are a different animal.
One known case of disintegration re flutter/harmonics of as fixed wing is the early Lockheed electra- several were lost. After finding out what really happened, the related problem was fixed- and a few dozen/hundred are still flying after 40 50 years - they afre called navy P-3.
The onset was due to a faulty engine mount design which came loose after hard landings. This allowed the turboprop engine- turbine to go into a whirl mode ( via gyroscopic action) at what was the natural frequency of the wing. In a few seconds, the wing ( VERY STIFF ) disintegrated.
That was in the late 50's as I recall.
AS to 777 - not impossible - but IMHO VERY unlikely !!
Simply too much redundancy and a flexible wing.
And NO its NOT like galloping gertie issues...