Sorry, forgot to ping you to my previous message.
The Vice-Chairman of the committee that heard Butler’s testimony was later revealed to be a Soviet agent (probably more for the money than out of ideological conviction, though).
There was definitely an interest on the left in building the story up to be a major indictment of capitalism and the millionaire class.
Interestingly, some of the closed door testimony has never been made public — or presumably, found. Make of that what you will.