If I recall correctly (an iffy proposition) William was given areas that would mesh with what he would take over when he became Prince of Wales. That makes all the sense in the world, to keep the eventual transition as seamless as possible on every level. Harry wanted a bigger role and was told no, that's for William. So understanding this, we know the split between the brothers has been brewing since before TOW. Harry had talked about being the third wheel about the time the (then) Cambridges started Heads Together with Harry. He said something to the effect of not wanting to be a hanger-on, wanting to establish himself as doing important things in his own right not just as the younger brother.
While I do think that Meghan has brought out and encouraged the worst in Harry, it was already there waiting for the flames to be fanned. It's very easy to blame her for everything but, as I've said before, Harry never told her to slow her roll or to stop badmouthing his family. He missed every red flag and clanging siren when it came to her, but that's on him. A different kind of woman would have encouraged Harry to heal the hard feelings with his family and carve out a niche that made him happy. But really, I don't think he'll ever be happy.
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