I think we should wait until we hear more of the official investigation before we start discussing who was to blame. Accidents tend to have many causes, and even if someone seems oviously to blame it might not be the case, or might be a fairly minor factor. It doesn't stop scapegoats being made of them though. Even excess speed can be caused by many factors which are outside of the drivers "blame" (e.g they might have become ill). Admittedly though it is more easy to think of ways where the driver was at fault, and many alternatives to the being at fault are really clutching at straws (e.g some kind of run away). Accidents are usually caused by rare combinations of circumstances though, so nothing can be rules out.
One thing to think about. Many people on both sides of this discussion are very quick to attribute blame to the driver in incidents involving road vehicles on railway lines etc. This is no more right, since again there can be many factors. Afterall, trains, cars, etc, are drivern by humans, and humans make mistakes. Oviously if negligance is found in any case (in particular drink, drugs, excessive tiredness or a disregard for the rules), the book should be thrown at them, although sadly often the worst get off lightly, sometimes ending up no worse than a pure accident. We don't give a good impression of the railway industry if we go by the view that those inside are always right and those outside are always wrong. We just end up at bad as the media, pro-road/anti-rail groups etc.