Here is a good analysis on the Church’s position on nuclear weapons from Pope Pius XII through Francis (yes, the article is from the SSPX, who are in an irregular canonical situation and working with the Church to resolve, but it is a good, brief explanation nonetheless that defends Francis on this point).
https://sspx.org/en/news-events/news/pope-says-“no”-atomic-weapons-29450
If you don’t want to click the link, basically, Pius XII was first completely for disarmament as nuclear weapons were always disproportional in a just war analysis, and therefore we would have to choose to suffer injustice rather than use them. Through the papacy of St. John Paul II, the Church accepted possessing them for bilateral deterrence as an intermediate step to disarmament–this toleration was mostly due to the need to maintain the political stability between the two superpowers with the world in a state of bi-polarization. With the breakdown of that situation, Benedict XVI and Francis returned to the earlier position of Pius XII.
Since it is a factual analysis, I think a politician could disagree in good faith and consider that we are still in that intermediate step where ownership can be tolerated for deterrence–but he should be trying work for disarmament.