One of the main reasons, I suppose, why the obvious way of reading the chapter has been ignored for so long must be the fact that in a good deal of Christian theology the fall of Jerusalem has had no theological significance. This has meant not only that Mark 13 is found puzzling, but also that all the references to the same event elsewhere in the gospels -- even where it stares one in the face, as in Luke 13:1-5 -- have been read as general warnings of hellfire in an afterlife, rather than the literal and physical divine-judgment-through-Roman-judgment that we have seen to be characteristic of Jesus' story.
N.T. Wright Jesus and the Victory of God pg. 343-4