The point about lorries driving illegally is that it is dangerous and illegal: if you are driving in this manner you are both more likely to cause accidents and less likely to report them.
Illegal driving includes reversing the wrong way down one way steets; driving and parking on pavements; parking obstructively; driving recklessly fast. They have clear delivery instructions that they disregard.
Nobody blamed them for "Sainsburys inaccurate forecasting of likely traffic"; your point about narrow streets does not tally with Sainsbury's themselves regarding the store as notoriously difficult to service. The fact that lorries also cause problems in other communities does not seem to have much bearing on this.
Why should the community bear the cost of damage and increased insurance premiums let alone the threat of injury rather than Sainsbury's?
Sainsbury's know about the problem but do not deal with it effectively; there are cctv cameras; they consider that to admit any liability or take responsibility would have more impact "on their shareholders".
The point about "the kind of horrific accident described earlier. The truck driver had no idea either that it had happened" is surely that it is essential that a zero tolerance approach to poor lorry driving is adopted; an "ordinary motorist" is far less likely to cause this sort of accident.