Russell was a nutcase from day one.
In the beginning he was a harmless and semi-wealthy nutcase. Although the records state that he was wealthy in his own right, the fact is he and his FATHER made a lot of money, and once that business was sold and the money distributed between father and son, there's no evidence Russell made any more money ON HIS OWN except through Watchtower.
By the time his wife Maria sued for divorce (after 18 years of marriage) Russell was a raging lunatic. He had written two of the studies in the scriptures, and try reading them, there aren't many mental illnesses this man did NOT qualify for. Maria tried to help. She was responsible for some of the writings of the Watchtower (she was the one with the college education and teacher's credentials) and she moved to protect the magazine from Russell's rantings, but he had her kicked off.
Rusell said Maria was controlled by the Devil; that going against Russell she was going against God himself. Russell told everyone MARIA was sick; wrote letters to everyone saying MARIA was to be shunned. Typical of many persons with histrionc, paranoid, delusional, persecutional and narcisstic personalities, he turned on the person who loved and helped him the most.
One day Maria had had enough. She climbed through a window and ran for safety and protection to her family in another city. She never went back. She went on to sue Russell for over $9,000.00 (in 1900's value) that was paid for by his followers.
Ego - Maniac is a very everyday ordinary word to describe someone as ill as Russell was.