A traiter, Felt, to the US should not benefit from his crimes.
No argument from me, but you can tell by looking at the guy's eyes that his brain died a long time ago. I mean that literally.
The whole reason this came out now is because he is about to croak.
A secondary reason might be to provide cover for the other traitors who leaked info to Woodward. I believe that "Deep Throat" was a composite of several high-ranking federal scumbags. Some of the info that Deep Throat supposedly provided would not have been available to Felt.