Outside the United States and certain very Americanised circles elsewhere, everyone had simply assumed that the Catholic Church had been against capital punishment for about as long as most people could now remember.
But this was a slavery situation: the theological logic has always been against the death penalty, just as it was always against slavery, but various factors had conspired to make it necessary to guide people towards that inescapable conclusion until they had all made it to the end at their own respective paces.
Eventually, though, that was just not good enough with regard to slavery. The Americans might never have got there. And it has turned out to not to been good enough with regard to capital punishment, either. The Americans might never have got there.
In any case, Catholics, simply as such, have been and remain among the world's great victims of the death penalty, and not least in England or under English rule. We are among the many categories of people with no excuse for any hallucinations about the necessary, or even the normative, benignity of public school Anglicanism when it is expressed as public policy.
And what even of those who do come from that tradition? Like every actual or attempted erosion of civil liberties, never welcome capital punishment unless you are absolutely certain that it could never happen to you. If there are people who can have that certainty, then they do not include traditional conservatives in the English-speaking world.