Is it possible that you don't know that the British Royal Family is a business? Is it possible that you don't know that Princess Di was the daughter of John Spencer, 8th Earl Spencer? That means she grew up in the peerage and should have known exactly what her position was. Hint: that means they don't marry for love.
She agreed to fealty under the Queen and her son. She could have said no to the Crown Prince Charles, instead she grabbed for the brass ring expecting it to be golden, cha-ching! That pretty much made her a gold digger with stars in her eyes, in spite of the long and sordid history of the British Royal Family. She was a fool, a fraud, and a liar before anything Charles might have done.
I probably know more about it than you do. She was a damaged 19 year old romantic. He was a jaded, privileged 30 something being pushed to have an heir. Did you know they sat together on a couch and cried after their divorce? Nothing is ever black and white. All humans are frail with faults and failings. Some people forget that in their own perfection.