Why Godfrey Cass left Molly Farren when he loves her?And why he again fall in love with Nancy Lammeter?According to me one person falls in love only once in life,isn't it?

Yes Godfrey married molly farren earlier.but after his marriage he realized that she is a girl of poor reputation and he can't introduce her in the society as his father wouldn't accept her so he didn't gathered enough courage to tell Mr Cass about it.he wanted to get rid of her anyhow.

For his father he was unmarried .he also assumed that he has to make a second marriage with a girl who can match upto their class and his father would accept her too.there was no better option than Nancy lammeter and he already liked her and wanted to marry her.

And for the last QN ,according to me a person falls in love only once. And I do think he didn't loved molly farren .if he did then he would not let her in such bad situations and would surely accept her in the whole society