I think "settled law" means something that people can live with, civilly, even if most of us disagree. Loving v. Va ended anti-Miscegenation laws, but most states had gotten rid of them anyway. Similarly, the Sup Ct has said repeatedly that once a vast maj of US states find the death penalty is cruel and unusual punishment, they'll "kill" the issue for all. (-: Conversely, Roberts warned that gay rights folks were getting ahead of themselves with gay marriage.
imo, the Roe Court just misjudged the political climate and thought Roe would become overwhelming popular and end total abortion bans nationwide. They simply miscalculated how fervently a minority of Americans would hold onto their belief as to what Christianity requires on the particular issue of abortion .... and that view of Christianity was never uniform, btw.