I could see two factors going on. One is that valid marriage vows cannot be conditional. That can be an impediment to marriage right there. The other is that while the choice to sin is not an impediment to a valid marriage, the inability to make mature choices necessary for married life can be.
I can’t see where the wife’s condition would have been an impediment to her getting married. We all have faults which we fully intend to overcome, but which are not easily defeated. If that doesn’t come under “better or worse”, I don’t know what does. Unlike alcoholism, nicotine addiction generally does not rob a person of their faculties for performing work, treating other people with charity, and answering other duties.
The husband, on the other hand, says that he made his vows conditionally. That makes their validity problematic, unless a review of his understanding of his vows at the time of his marriage makes it clear that he knew no such conditions could apply, yet consented to marriage anyway. In that case, saying, “I told her I wouldn’t marry her unless she quit smoking” is a hyperbole, an overstatement of the truth that he and she both agree that she needs to make efforts to quit.
He may also be claiming that he does not have the maturity to fulfill his marriage vows in spite of his wife’s faults…that is a stretch. I don’t buy it. We all marry sinners, and they marry birds of the same feather. That we are not saints does not make us incapable of valid marriage.
