David - who heads the sci-fi cult, of which Tom is a devotee - was best man at the couple's wedding, and sources have claimed their intense Friendship is one of the reasons they grew apart.
A source told The Sun newspaper: ''Miscavige and Tom are joined at the hip. Tom runs every important decision in his life by him.
''Tom really values his opinion and Katie often felt like she came in second place. When it became clear how much influence he had over her husband she knew she had to get away.''
David is said to have given many lavish gifts to Tom, including an aircraft hanger for his private jet and a custom-built luxury coach.
Katie, 33, filed for divorce from Tom last Thursday (28.06.12), and one of her reasons is because she feared their six-year-old daughter Suri would be heavily influenced by Scientology if she stayed in the relationship.
Insiders say Tom - who has been married three times - moved away from Scientology during his union with second spouse Nicole Kidman, but when they split in 2001 he turned to the organisation for guidance.
A source said: ''Nicole was really sour on Scientology and kept pressing Tom to stay away.
''She spotted Miscavige and didn't like what she saw. Her big issue was that Tom was becoming like Miscavige. Nicole didn't like the relationship that was developing between them.''
Katie was raised a Christian, but did partake in the Scientologist practice of 'Auditing' - a process which sees an individual confess their life experiences to an auditor in a bid to free themselves from unwanted psychological barriers - although ''she was never completely committed to Scientology, but participated because she was in love with Tom and knew it meant a lot to him''.
Tom flew back from Iceland to the US yesterday (03.07.12) to celebrate his 50th birthday.
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