People saw this and correlated it to the announcment of Pope Francis.
It seems like a casual coincidence to those who are not prone to find particular meaning in these things. But these types of correlation have powerful meaning to those of faith or serve as “signs” for those who interpret it in their own way.
There is no reason why an angel shaped cloud would appear just in this place. It is an interpretation of a shape in accordance with an event of personal significance. It’s very pretty. A person who has lost a loved one would find a different meaning in it from those who have a sick child or from weather watchers.