Because Harry has always been treated worse than William
The biographer of the royal family has no doubts: Harry has always been treated worse than William.
"I would say that William was always treated with more benevolence than Prince Harry was ever treated, but that was the fate of the second sons." To reveal it, in no uncertain terms (and with extreme confidence) is the biographer of the crown Robert Lacey on the podcast, Pod Save the Queen.
According to the expert of the royal family, if while they were children Harry and William have always had the same attention, growing up however the Duke of Sussex has seen himself gradually being put in the background. "Harry sadly followed and follows, sadly, the tradition that struck Princess Margaret and Prince Andrew as second arrivals, who were treated harder according to the logic of the monarchical system that still favors the main bloodline today."
The reason? The progressive descent in the order of succession: "If before Harry was the first after William for the succession, now he has gone down and will go down to sixth, seventh, eighth place and so on". In fact, with the birth of the royal babies, George, Charlotte and Louis, Harry currently occupies the sixth place in the line of succession and could climb even further when William should have another (or another) heir.
Indeed, looking back in time Harry was the only royals to have to publicly apologize for his mistake (although it was more than necessary given the circumstance) and, despite having always been considered "Elizabeth II's favorite", at at the same time he was not protected, at least by the royal staff, as much as William was against the attacks of the tabloids. That the decision to divorce the royal family and, in general, the logic of the monarchy is also the result of this?
