. The pictures show that all the blades on one of the turbine wheels have lost the outer one third. They look as if they have melted away.
Roughly 2/3 of the stresses on a turbine blade are centripetal. The remaining third is thermal and bending, focussed on where the blade meets the root. It doesn't take much of an overspeed to cause significant creep (especially at close to maximal operating temps). Blade life is usually a function of creep burst (the blade stretches as it's life goes on).
And yes, any overspeed is likely to take the entire assembly into resonant modes that may result in untold High Cycle Fatigue and ultimately failure. It is likely the remainder of the blades was scraped off in the casing of the hot section as they stretched like toffee.