Even though Prince William is the rightful heir to the British throne, Princess Diana thought that he didn’t quite fit the part, but instead her son Harry would be better.
All things considered, right now Prince Harry is only sixth in line for the throne, in front of him are his brother William, his father and William’s three children, so Harry probably won’t get the chance to be the king. Allegedly Princess Diana thought that Prince Harry would be a better king than Prince William.
In her 2018 biography Harry: Conversations with the Prince, Angela Levin goes into Diana’s relationship with her son. Reportedly she Diana noticed that Harry had qualities that would make him a good ruler as he was growing up. Although William was the rightful heir and older Harry had qualities that make a good leader like, “ability to cope”, “ease with people” and “general gusto”. A lot of fans of the Royals can still identify some of those characteristics in Harry. Allegedly Diana nicknamed Harry “Good King Harry”.
As far as William goes, she didn’t think he would make a bad king but that she thought he didn’t really want the throne since he doesn’t want his every move watched.
All in all, this was all when Prince William was much younger, he’s changed over the years and has a new outlook on things. He will surely make a great king once his time comes. And as for Harry, it’s better this way since he said that he doesn’t want the throne.