The public also criticized the monarchy for being cold and indifferent.
But in the past year, Prince Charles has shown great care for his sons, observers of the royal family say.
"I think he's done actually extraordinary well," Dr. David Starkey, a British constitutional historian, told CBS 'This Morning.'
Starkey says the change in Prince Charles began within a few days of the princess's death, when the British paper, The Sun, featured a shot of the new widower with his son, Prince Harry, in front of the gates of a church. In the photograph, the boy was reaching up to his father. The headline read "Safe in Dad's Hands."
"This has been the transformation in people's perception of Charles. He's a good, caring, involved father," Starkey says. "Very different, it has to be said, from his own mother."
The two young princes impressed the world with the way they handled their mother's death, publicly greeting mourners who had stood in line for hours to sign books of condolences.
"I think they wanted very much to prove to themselves as well...after their mother died...that they could do it, that they wouldn't break down, they would do well," says Ingrid Seward, editor-in-chief of Majesty magazine.
Seward says that Prince William has worked hard to achieve his "A" grades, and that every effort he and his brother make is for their mother.
One year later, there is much debate about what Diana's legacy will be as time moves forward.
Starkey says that Diana's legacy was "actually quite small. There have been a few trivial changes in the monarchy."
Queen Elizabeth, distraught by the critical reaction of the people, hired a publicist to help her and the royal family with their public image. She was advised to behave more like an average citizen.
In March, she went to a pub for the first time, held a party for celebrities at Windsor Castle in April, and visited a McDonald's in August. The response from the public has been positive, Seward says.
On Monday, the queen thanked people who have sent messages of sympathy, through the royal Web site as well as in the mail.
In the past year, the British monarchy has also welcomed the estranged princess back into the fold. As a result of the royal family's embrace of Diana, the monarchy is riding high in the public opinion polls.
Some of Diana's staunch followers are unhappy about the sudden change.
"They are Diana's true army. They believe Diana represented something opposed to the monarcy," Starkey says.
"When Prince Charles went over to bring the coffin back from Paris, he sort of remarried her. When Diana was buried under the standard of Royal Highness, she became sort of royal again."