If they were still on the ground after leaving the end of the runway and in a tailstrike attitude, it does somewhat follow that they weren't going fast enough to fly at that point (less than Vmu). What *could* cause this on 12,000' of tarmac?
- Lack of thrust
- Not enough flap
- Too little runway (intersection departure)
- Windshear
- Gross overload
Something (or things) must have gone badly wrong... After all, the aircraft should have been able to clear the runway end by at least 35' after losing an engine at V1. I doubt this accident has a type-specific cause as it is so far removed from normality.