Yes. He didn’t do it on his own, though...that directive came from above. It was a general amnesty. (and I generally dislike MacArthur)
I wasn’t alive then, but the mood after the war was, in some circles, to move as rapidly away from it as possible and forget about it.
An egregious example of this injustice was described in the book and movie “Unbroken”. The prison guard officer who murdered men faked his own death, but came out into the open and became a successful businessman after the amnesty.
The doctors of unit 731 went back to join the Japanese medical establishment. They were all successful. One of them became head of Green Cross. A war criminal was elected prime minister. A thousand war criminals were put in the national shrine at in Yasukuni temple. Including the guy in charge of the rape of Nanking.
Our perspective of what should have been done versus what was done has to be informed by what was going on at the time. By the time of VJ Day, we could already see the outlines of the next war against aggressive Communism as sponsored by Stalin and the Soviet Union. In Europe there was the exhaustion of resources and the masses of 'displaced peoples' (DPs) that kind of locked the borders where the Armies stopped.
In Asia, within months, the last-minute entry of the Soviet Union was causing 'problems' in Korea & Manchuria while the Chinese Red Army moved almost immediately against their internal rivals of the Chinese Nationalists. The need for rapid 'pacification' of Japan became a priority while also modification of its society to destroy the Bushido / oligarchic culture within Japan.
History is always all kind of shades of gray and what comes in war's aftermath frequently has many of the darker shades. An example of horrible acts from Europe at this time was the forced repatriation to the Soviet Union of hundred of thousands of people who had no desire to go when they KNEW that they were looking at prison at best.