Showing Respect
This theory seems to be popular, at least with regard to the British population. In fact, according to a survey that StatistaCharts conducted for The Week, nearly 50% of the British public want to see William accede to the throne instead.

Showing Respect
The Proceedings
Allegedly, Diana had mixed feelings about Charles becoming the monarch. This should not come as a big surprise as their divorce did not end really end well. In 1995, she addressed this when she made an appearance on Panorama.

The Proceedings