Cambridge’s low crowd got me googling low second tier/Football League crowds which led me to this: https://talksport.com/football/efl-cup/122663/24936/#:~:text=Some reports suggest that the,had a capacity of 100,000! Anyone going in 1962?
Ten years before that match Cambridge were in the Southern League, they rarely got 2,000 in that league. The 80s were the decade when crowds dropped dramatically, mainly through crowd trouble. Looking at all those gates our average this season beats most of them, 8,000 for the Scum and 11,000 for the Massive are a joke...