I think his hatred and distrust of J. Edgar Hoover had a lot to do with his downfall as well.
What I find particularly appalling, aside form the fact that the Commieposts Owners having a tight social relationship with Hiss, and vowing years later to Bring Nixon Down, was that the chief instrument, was Rodino from N.J.
Imagine the absolute Gall of that, A Democrat Politician from NJ calling someone corrupt.