It was a pleasure watching James' videos on YouTube. Rest in peace, brother triker.
I lived in Southern Mississippi many years ago and am familiar with this road. Straight road with good sight lines. Hard to believe that a driver paying reasonable attention would not have seen him. Still, things happen quickly at (and probably above) the posted 65 mph speed limit.
Edit to add this: There is a YouTube video of one of the witnesses who said that the driver that hit him probably did not see him because his view was shielded by another vehicle who swerved at the last minute.