Cracked Kellogg's Cards That Have No Other Damage

I picked up a set this week that must have been a factory set.  I never had the money to buy one of these as a kid.  That didn't stop me from getting the entire 1974 set the hard way - cereal and trades.

Back to the set I picked up.  The 1977 set was advertised as all being cracked and every card was.  I have no complaint about this set at all.  Actually it was probably better than I expected for the price I paid.



I'm okay with cracked cards.  I am even assembling cracked sets myself.  The surprise was that every card looked to be from a factory set.  All had nice, squared corners and a consistent look to them.
None of these cards are curled either.  They appear as though they have been in a stack since 1977.

I've seen sets where the top cards, or the top nine cards if in pages, get cracked.  How does it happen that every card gets cracked?  Any ideas.



The card show below was not included in the set.  This well-loved card is similar to those I am  using to build cracked sets.  It has lots of damage beside being cracked.