"Fancy Tybalt's being a bridegroom! We always thought he would never marry! He's married to all that nonsense, Nanny Tester says. 'Like your father ought to have been.' I used to point out to her that if Papa had married all that nonsense I wouldn't have been here nor would Tybalt because archaeology, wonderful as Papa and Tybalt seem to find it, does not produce people, living ones anyway. Only mummies perhaps. Oh, do you remember the day when you dressed up as a mummy? What a day that was! We thought you'd killed Theodosia."
all that nonsense?
Not a teacher.
He's "married" to his work. In this case archaeology. The nanny, in this excerpt, doesn't think much of the science, hence the use of "nonsense" to describe it.