I would suggest that as the nose impacted the ground and broke away, the forward part of the fuselage remaining dug in and inertia carried the rest of the aircraft up and over and into an inverted backwards slide.
The important thing to realise in relatively high speed impacts is that while the forward part of a vehicle (aircraft in this case) may come to a complete rest, the remainder of the vehicle is still moving with essentially the same forward speed and inertia. It is this phenomenon that causes bullet splatter with small projectiles, crumple zones to work in motor vehicles and substantial parts of an aircraft fuselage to split away and carry along a debris track from the initial impact site.
Think in terms of dropping an extended slinky spring onto the ground. The bottom of the spring hits the ground and comes to a stop, while the top, or tail end of the spring is still travelling and accelerating downwards.
It takes a finite time for energy to propogate through a structure. In the case of the slinky spring demonstration, the majority of the energy is actually provided by gravity, not by the spring attempting to contract.
The nose breaking away is an indication that this section stopped almost instantly while the inertia of the remainder of the fuselage was sufficient to flip and slide a considerable distance further on.
Your video assumes and essentially wings level initial impact of the fuselage section with the ground. I suggest this is inaccurate and a substantial bank angle was maintained after contact with the railroad embankment. That is the only way the aircraft profile would have been able to pass between the trees. It is also more likely to result in the tail section being upside down and facing the direction of travel.
The aircraft could have impacted wings level, the nose broke away and then the remainder bounced and flipped over the trees, but this is a more complex scenario and therefore less likely to have occured.