The problem is negligence, or negligent homicide. Also, looking back through the thread, speeding, although that may be hard to determine accurately.
So, if this was a fluke accident... then no prosecution.
If the driver knew he had a serious problem with his vehicle and chose to ignore it, then that pushes one towards negligence. Also an improperly loaded trailer.
What would an ordinary competent driver do in the situation? Drift towards a concrete wall, and my first reaction would be steering AND BRAKES. Drift towards over a dozen cyclists, and my reaction would be to mash the brakes like there is no tomorrow.
If the driver was initially passing from the left lane, then that is good, although as a cycling driver, I like to slow down when passing pedestrians and cyclists. If I can't safely pass, then I'll slow or stop until I can.
This whole thing sounds more like a distracted or dozing driver than anything else. And the law requires safe operation of a vehicle one is driving. One can argue about the details, but one must drive safely per the road conditions.