I think Harry and Meghan were two people in a particular frame of mind who met at at time when only disaster would ensue.
Harry: desperate to settle down, flailing about for purpose when W&K were finding theirs and starting a family, also a spoiled and entitled brat who wouldn't follow guidance for just/unjust cause
Meghan: hustled her entire adult life to reach heights she'd dreamt of since girlhood, seen and deployed every trick in every book to get where she was, met Harry and saw him as a golden ticket.
Harry, eager to bag Meghan, over-promised: we'll do this and that, don't worry I can get him/her to do whatever I want, you're amazing and I love your vision for a future for me, you remind me of my mother.
Meghan: everything you're offering me is what I've been looking for, I'm going to be #1 FINALLY, I can make it all happen if you just believe in me and only me.
Meanwhile, advisors and agents and PR reps (all paid, all personally motivated to fluff up H&M because they'll get a cut) are whispering words like "$100m deal", "world's most glamourous couple", "worth $1bn", "$1m per Instagram post" into their ears. Oprah wants them, Beyonce and Jay-Z line up to shake their hands. Palace staff are there to do things for them that they'd had to do themselves (Meghan, at least). Designers are throwing clothes and goodies their way. Journalists are all over them. Acres of newsprint written about them, photos everywhere. They barely spend a few months in the same place at the same time, then engagement (with $56,000 dress for a photoshoot for her), then royal wedding preceded by family drama, then HMQ this and W&K that, then housing, then pregnancy, then then then...
They lost their heads. Got caught up in it all, believed everyone's and their own BS, let their egos swell - and here they are. Two kids, largely disdained, exiled, no means of sustaining themselves financially to the level they need and want, estranged from all family and many friends, having revealed themselves for the unintelligent, not-as-wily-as-they-thought, vainglorious, messed up adults they are. You almost feel sorry for them, but they chose this and actively chose to ignore those knew better.