This was most likely due to (predicted) weather on your route or at/near the destination. There could also be mechanical issues that can weight limit a flight.
Originally Posted by
inthecloud
Delta Cargo makes money just as revenue flights do. Could be some heavy cargo for a high paying customer who needed LAX-ATL at that time, maybe bumping passengers was still profitable.
Cargo makes up less than 2% of DL's revenues. Domestic cargo rates are quite pathetic. It would cost much more to cut pax than to cut cargo.
If they had cargo that needed to go to ATL, they would have simply cut it and put it on the next flight to avoid a weight restriction. There are plenty of LAX-ATL flights.