It is different because Gatsby is not married to anyone. Gatsby committed adultery by lusting after a woman. In Matthew 5:28 it says “But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.” (New International Version) Since Gatsby lusted after Daisy he also sinned.
Tom hates Gatsby. One reason he hates Gatsby is because Tom sees that Gatsby is trying to steal his woman away from him. Another reason is that he believes that Gatsby got his wealth from illegal activities like bootlegging. “He and this Wolfsheim bought up a lot of side-street drug-stores here and in Chicago and sold grain alcohol over the counter. That’s one of his little stunts. I picked him for a bootlegger the first time I saw him, and I wasn’t far wrong.” (Fitzgerald 133)
The feelings between Tom and Gatsby are mutual because he hates Tom. The reason that Gatsby hates Tom is that he married Daisy and Gatsby feels that Tom is not good enough to be Daisy’s husband. The reason that Gatsby feels that Tom is an incompetent husband is because Tom is cheating on Daisy. Since Gatsby loves and he believes that Tom is not good enough to be with Daisy Gatsby tries to make Daisy leave