I assume Cancellara et al wanted to give as many folk as possible the chance to get back into the main group or at least minimise their losses. Nobody wants the most important race of the year decided bacause of a crash that was caused by oil on the road.
I am a little puzzled (just as many posting here are) as to why there is so much concern about the course itself

If it hadn't rained would there have been a problem? (with the oil yes but with the route?). I know it's narrow and twisty but...
It seems to me that the riders are not all agreed about that some feel it was inappropraite others seem fine about it.
We'll see what happens tomorrow!