Possible, but we don't know this for certain. We don't know when the load shifted, we don't know how the mirrors were adjusted, we don't know how attentive the driver was to his right hand side view mirror.....
Unlikely that a DA would think they could make such a charge stick. Sadly, drivers get acquitted even when the circumstances and evidence are much stronger.
I have driven many large, medium and small vehicles for work. I never allowed excuses to endanger others. I don't believe the driver of that vehicle had no clue about the wood hanging out off the side of that truck. There is a level of responsibility that a competent driver adheres to. This driver did not take the time to properly secure their load. If the problem really couldn't be seen then the mirrors are improperly installed and the driver was illegally driving that vehicle. This kind of incompetence is rampant in the USA because we expect these kinds of things to happen.