It is easy to dislike Ted for this, but I think this sort of thing happens a lot to partners who have sick partners. It is a huge strain on the relationship and the care-taking partner can often feel like a victim. After all, nobody really checks on how the illness affects them and it can feel like they are trapped.
Consider also that it sounds very noble that she sacrificed everything for him, but was that what he wanted? A sacrifice can be selfish if not done with consent of both parties. This was especially hard for women at the time because a divorce didn’t just mean the end of a relationship, it also often meant the end of their life (figuratively, but sometimes literally). Patriarchy bound women to men in a way both parties were trapped by.
Monogamy is hard, even without illness. Communication is the thing that keeps relationships going and even today people are bad at it. In the time they were alive, I don’t think they even had real models for what good communication should look like. This isn’t to say Ted was blameless, but I also won’t say that he was a monster for this.
Sure, and I agree with that. None the less, my point is that these things are very easy to see in a black or white lens, but they are usually a lot more complicated. Ted isn’t innocent here, but neither is she. They are both victims of the patriarchal society and of each other.