https://www.jwfacts.com/watchtower/mediator.php
Religions do not volunteer their most offensive doctrines to newcomers, and Watchtower doctrine about the mediator generally is not presented to Bible Studies before baptism. The word mediator does not appear at all in What Does the Bible Really Teach?, a primary teaching aid of Jehovah's Witnesses. Yet Jesus role as mediator is an important and fundamental teaching of Christianity, directly discussed in the Bible. In the Reasoningbook the only mention of the mediator is in an unrelated manner that attempts to explain why we should not trust in Saints;
"1 Tim. 2:5, JB: "There is only one God, and there is only one mediator between God and mankind, himself a man, Christ Jesus." (There is no allowance here for others to serve in the role of mediator for the members of Christ's congregation.)" Reasoning From the Scriptures? p.184 par. 7
That is an ironic statement, since the Governing Body claim the Great Crowd benefit from Jesus role as mediator by being in contact with them.
Watchtower hypocritically criticises the Catholic teaching that Saints can be “intercessors with God”, quoting 1 Timothy that there is only one mediator, yet the Watchtower teaching that the anointed mediate for the Great Crowd is in the same vein as this Catholic teaching.
Watchtower 2014 Jun 1 p.15
Jesus acts as both Mediator and High Priest. He is mediator to all mankind, with no intermediary between himself and humans. No man is our head; everyone answers directly to Christ.
1 Corinthians 11:3 "But I want YOU to know that the head of every man is the Christ"
The Watchtower teaches that only 144,000 people make up the New Covenant, and that Jesus is mediator for them alone. Of the billions of people that have ever lived the New Covenant is only open to 144,000 people, around 50,000 of which lived in the first half on the 1900's.
By saying that Jehovah's Witnesses can only have a relationship with their Saviour if they are united with the Slave Class, Rutherford transferred tremendous power to himself and the following leaders of the Watchtower Organization, effectively creating the structure necessary for (and indicative of) a cult.