Also I think William was likely thrust into the role of 'my brother's keeper' during their teen years and early 20s as Harry by his own account was unstable.
It interests me that Harry would rather be seen as unstable than dimwitted. Around about the 20 years of age mark was when he really started hating the press (all of it, not just 'the tabloids') because he kept engaging with them, and they printed what he said, and some of it looked terrible, and so he hated the press, and he's been going round and round and up and down like Sisyphus ever since.
Instead, he could have worked with the royal family's press office to come up with a simply strategy of 'no commenting' when, say, asked about Chelsy Davey. 'I will not comment on private matters nor will I comment on a private citizen.'
Rather than do this, he fired off some really awful, stupid responses, the most infamous of which is, 'She's not black or anything, you know.'
(I'm quoting that, btw, from an archived Guardian article by Ben Summerskill (Jan 2005), not a 'tabloid'. It's really gossipy article and a bit of a weird read, given the passage of time, but I think Summerskill's quote is accurate.)
https://www.theguardian.com/g2/story/0,,1383309,00.html