The bus driver would probably get into trouble if he delayed the bus, he couldn't be expected to risk his job.
And to be fair - his milk of human kindness has probably been eroded over god knows how long of dealing with drunks and taking abuse while trying to do his job and drive the night bus.
To us this girl is a shocking, horrific example of can and did go wrong, but for him, at the time - she was probably just another pain in the arse drunk person trying to pull a fast one.
I have no doubt he has faced all sorts driving that bus, a short drive through the town centre where I live at 2am to collect someone told me, dealing with the drunken masses at that time of the morning is absolutely not something I would want to do.
The rapist is to blame. The driver will probably be living wig his conscience for the rest of his life, but I do wonder hat he goes through in the course of going about his job to make him be so hard hearted.