re: So, why did the Iron Bowl take a 40 year break?

The facts on the Iron Bowl stoppage period:

Didn't play from 1908-1947.

BAMA's record during that time 266-74-20
AU's record during that time 196-136-10

National Titles during time-frame
BAMA - 5
AU - 0

Conf Titles during time-frame
BAMA - 4 Southern Conf, 4 SEC - 8
AU - 1 Southern Conf, 0 SEC - 1

Series record prior to stoppage - 3-2-1 BAMA
First game in the series restart - BAMA 55-0