Speculation at this point, however...
"Look at the skid marks to the right of the cars.... It drives home for me the idea that a truck picked the switch. It was likely the rear of the 2nd car. The front of the 2nd car pushed the 1st car off the tracks, and the 1st car twisted & lifted the loco, even one foot could do it, off the trucks, and it flipped over once it was not resting on the trucks properly."
Unlikely. There is no way an LRC coach could lift or twist an F40 off of its trucks, unless it already was airborne off of a bridge.
More likely, the No. 1 track switch was in the closed position (i.e. not lined up for a diverging route), and at 67mph, this would be enough for the F40 jump the tracks and keep going on its diverging route (straight off the right of way and into some buildings). The train seems to have made it through the first switch on its diverging route (leaving track 2 diverging onto track 1), but failed to negotiate the second half of the interlocking.
What a horrible way to go, for everybody involved.