Why were the boxing matches between joe louis and max schmeling such big stories internationally

Because the match it's not a simple bout between athletes. It represent proud and nationalism from both countries that involved in the cold war.

At that time, America and the Soviet Union competed at almost anything to show the world which has the better system.  Joe Louis was the boxer that represented America, while Max Schmelling was chosen to represent the Soviet union.

it was bribing i think i might be wrong though