“Why waste all the perfectly good intelligence, insider-political knowledge and operations ability?”
Ask the hundreds of thousands they murdered in cold blood. Ask the women they humiliated, stripped naked and shot into a muddy ditch. They had nothing that important that they shouldn’t have seen a rope.
In fact, many of them exaggerated things so they could save their necks from the rope. If you have nothing valuable, you aren’t worth saving.
You are so righteous, but I am sorry, that’s NOT how the real world works, nor how it has worked in history - including our beloved OSS/CIA after WWII.
Standard procedure is to hang the leaders, and sift through and co-opt what remains.
The USA/allies “purged” or investigated something like 4-5% of the German adult population after WWII
In Japan, that number was miniscule - something like 0.2%. We left their political-economic structure in tact, and basically took over the top positions
And you can argue the Japanese government were far more murderous than even the Nazi were and deserved hanging even more. But that’s not what we did.