Slight problem with that list of very important people from Kings to Cromwell etc is they are all very, very important people in our history.
Harry is a nobody. He never was going to be anybody in the monarchy or the future history of the monarchy. His name is forgotten in just one generation - gone.
He's not in line for anything, he's the younger brother and every generation there is upset that they don't feel special anymore and jealous of the new family line going (in this instance now going dow through George).
From Richard III and some young princes - to Harry - there are always siblings that think it should be done their way.
It isn't a big deal resigning (he isn't in line to be on the throne, and no-one would want him if he were).
He needs to the get the hell out properly and stop using the HRH etc
It should be noted William has made it known that he doesn't feel trapped by the idea - it's a role he's been preparing for etc.
To see the look of fury on Harry's face when he has to step behind William is shocking. Harry is furious that he isn't as important as William and his family, instead of coming to terms with that - he is embarrassing everyone and telling his wife it is racism.
The whole world are indulging Harry in his meltdown and upset at being the younger brother - some are believing it, I'm not - he wanted the "important" role.
If he can't have it, then he'll break the toy so his brother can't play either. He is that infantile. I see no evidence of anything other than a horrid selfish person that doesn't care about his family let alone the wider world's mental health.