They used to say that if you trod on a big dinosaur's tail, it would take several seconds for the signal to reach it's brain, so it couldn't react quickly.
I think some drivers have some dinosaur DNA in them.
That driver clearly committed to turning while you were hidden, and he wasn't able/willing to reassess the situation as it changed.
Of course he should have seen you earlier waiting to turn. I guess dinosaurs weren't good at forward planning either.