There's a lot more to it than that, of course. Harry is a fiercely intelligent, sensitive man who lost his beloved mother too early and was raised by a kindly but emotionally distant father. That makes him the odd man out in a bloodline bred not for intelligence, but for a phlegmatic nature, an utter lack of fear and the ability to stick on a horse as if you were born there!
His brother, Prince William, belongs in the 'nice-but-dim' category of good-natured, kindly, honest, sincere but beef-witted English squires (even if he is German). The Duchess of Cambridge is also of adequately average IQ. Even so, they lack the pathological dedication to duty which is so much a part of the characters of both the Queen and the Prince of Wales, and so have been criticised as 'lazy' for putting effort into their lives outside of Royal obligations.
Harry had been chafing under 'Royal' restrictions for years before he even met Meghan. His occasional 'unsuitable' behaviour as a young man, his insistence on serving in the front line and putting himself in harms' way alongside his comrades. His commitment to the proper care of veterans shows in more than just his support of the Invictus Games, and brought him into conflict with those who thought his stance too political.
The birth of William and Kates' children placed Harry out of the line of succession and made his choice of life-partner much more free. He chose a woman whose intelligence, fire and politics matched his own. But then they found themselves still trapped in the net of expectations created by the Queen, a steadfast opponent of any kind of change in what she sees as the role and duty of the Royal Family. Patronage of 'respectable' charities was fine, activism was not. There were foreign visits to be carried out, museum and art galleries to be opened, etc, and that is what the Sussexes were expected to do. Harry was having none of it any more, and, with a like-minded wife to support him, decided to strike out on his own.
The Press - not wanting to blame Harry, who had always been a favourite with the public - decided to paint Meghan as what an American friend of mine referred to as "Wallis Simpson v.2.0". They made much of her radical views, high-strung 'actressy' nature and supposed domination of Harry - not so much of her mixed-race origins, that was added by openly racist commentators on the Internet.
Me, I reckon it's mostly down to Harry, who always wanted to go his own way, but had never, until he married, had any support in doing so.