She seems to conduct herself with decorum and manners. She avoids controversy and does not try to attract attention to herself. She's a mature woman, and seems to know her role well. I've never seen a good explanation of why She and Charles didn't marry when they first met (and dated) in the early 1970s.
I think the view is taking hold that Diana, whose youth, beauty and naivete first grabbed people's attention, was also childish, emotionally immature and passive-aggressive. Certainly, it would take a truly exceptional character to be plucked as a teen from obscurity and placed into the cold and calculating world of the Royal Family.
whether you think these reasons are good cause..here are some of the reasons
https://www.goodhousekeeping.com/life/a20721800/why-prince-charles-didnt-marry-camilla-first/
he should have been with Camilla from the beginning. and i admit, not a Diana fan.
The story is that Liz didn’t approve of the non-virginal Camilla.