Because he dithered with Camilla, she got tired of waiting and married somebody else and made babies in the 1970’s.
In the 80’s Diana was chosen as broodmare whose sole purpose was to make an heir and a spare because Charles was getting long in the tooth.
Fast forward another decade Camilla gets divorced and takes up with Charles again. Diana, who now knows why Charles was such a cold fish, gets her divorce, but tragically dies because her driver was drunk.
Bottom line is Charles wrecked a few lives because he’s a not very smart fop in a position of privilege.
Camilla was not a virgin and was not of high enough birth. Charles was told that she wasn't suitable.
And he’s a liberal elitist to boot.