Prince Harry and Meghan Markle stole attention from Prince William and Kate Middleton, making them a major threat to the monarchy

• Meghan Markle and Prince Harry told Oprah Winfrey they weren't supported by the monarchy.
• It could have been because Markle and Harry's popularity outshone Prince William and Kate Middleton.
• Michelle Ruiz for Vanity Fair compared it to how Princess Diana stole Prince Charles' spotlight.

Meghan Markle and Prince Harry's strained relationship with the royal family has been in the spotlight since the couple's interview with Oprah Winfrey.

During the interview, which aired last month, the couple told Winfrey that members of the royal family made racist comments about Archie before he was born and that Markle was denied mental-health support when she was experiencing suicidal thoughts.

It seems counterintuitive for the family to have been unwelcoming of Markle when she was a senior royal, as she could have helped usher the monarchy into the modern age.

In Vanity Fair's May cover story, Michelle Ruiz wrote that Harry and Markle's relationship may have become an issue for the monarchy because people started paying more attention to them than Prince William and Kate Middleton.

Prince Harry and Meghan Markle's popularity overshadowed Prince William and Kate Middleton

Harry and Markle's popularity as a couple was not surprising. Harry was a handsome prince who had long been a bachelor, while Markle was an American actress who was famous in her own right.

But the world's love for them may have become a problem for William.

Anna Pasternak, the author of "The Real Wallis Simpson: A New History of the American Divorcee Who Became the Duchess of Windsor," told Vanity Fair that "Harry and Meghan were suddenly too electric."

Harry and Markle's glamour made William and Middleton "seem dowdy, suburban, and rather dull," Pasternak said, adding: "That does not go down well in the palace."

While all members of the royal family have some degree of fame, the monarchy tends to keep public attention on the monarch and those in the direct line of succession "for continuity's sake," Ruiz wrote.

So when Markle and Harry's relationship took focus away from William - who's second in line to the throne - and his family, the couple may have become a threat to the monarchy, rather than an asset.

"It's a no-win predicament familiar to women, and women of color in particular: You're either too much or never enough," Ruiz wrote.

Princess Diana faced similar treatment from the crown as her fame grew

Princess Diana was beloved by millions for her charming personality. At first, her public appeal was an asset to the royal family, but it quickly became an issue when she seemed better-liked than Prince Charles and the Queen.

Her popularity boomed after her first overseas tour in Australia in 1983, where she transformed into the "people's princess."

Charles, rather than celebrating her success as a win for the monarchy, became jealous, Diana told the BBC in 1995. And as Diana became more popular, the strain on their relationship grew.

Diana similarly upstaged the Queen at an opening of Parliament, Ruiz wrote. Her fame was viewed as a distraction, rather than something that could help the royal family.

Harry pointed out the similarities between the ways Diana and Markle were treated by the monarchy in the March interview with Winfrey.

He said the couple's own Australian tour in 2018 "brought back memories" of Diana's tour. Harry, speaking of Markle, said their tour was "the first time that the family got to see how incredible she is at the job."

From that moment on, Markle, much like the mother-in-law she never met, became a threat to the monarchy and may have changed the course of the royal family's relationship with the Duke and Duchess of Sussex for good.