Answer:
Because he left office peacefully and willingly.
By being the first president to leave office this way, he set a precedent and marked the first peaceful transfer of power between upcoming and current presidents. Since then, the loser of presidential elections has willingly and peacefully surrender power to the winner.
Truman may have fired MacArthur because Truman did not like having been previously under the order of MacArthur.
Code talkers transmitted messages over military telephone or radio communications nets using formally or informally developed codes built upon their native languages. The code talkers improved the speed of encryption and decryption of communications in front line operations during World War II