The A/C breaker in your TT probably tripped because the park's voltage had dropped because of the load from all the campers and that caused your A/C's motor to draw more current. Most likely the voltage drop on the 50A circuit was less because the wire gauge is larger and fewer people were on that circuit.
This assumes, of course, that the 50A and 30A circuits on the pedestal are fed by different wires which is the proper way to do the wiring since it is possible (although unlikely) that both the 30A and 50A outlets could be use at the same time. However, I am pretty sure that at many parks the 50A and 30A are not independent of each other and this argument would not be true.