Quite often the trucks stay on the left and then suddenly just go for it, and cut across the lanes. It's not always obvious that they're intending to do an u-turn. And it's the truck drivers' responsibility to check the road is clear before doing such move. My guess is that the pickup driver didn't expect the truck to make the turn, and once realised it it was too late to slow down on time.
But of course, it could be that he wasn't paying attention - often many accidents like these can be avoided with being alert.