I think it's a combination OP (and apologies for the essay that follows!) I think he always wanted out of the strictures of the official role of being Prince Harry, supporting the monarch and the institution. I think he found it stifling and hated the intrusion on his privacy. Fair enough - I think we can all understand that - and I think Meghan gave him an out, and that was part of her attraction.
But I think the plan that they cooked up between them to leave and make shit loads of money while still retaining all the benefits of being royal was half-baked and they rushed it and screwed up. They were beavering away behind the scenes for months before they left, setting up Sussex Royal and coming up with a plan to be global philanthropists, mixing with billionaires, PMs and Presidents with their royal titles and the blessing of the Queen, etc. But when Harry failed to get a private meeting with the Queen in Jan 2020, which he'd clearly counted on to persuade her to say 'Yes' without any advisors around, he was furious and felt utterly thwarted and I think most of what's happened since is a result of that.
I feel certain that he's still smarting about the loss of his royal status, his taxpayer-funded security, the ability to trademark their names and set up a foundation with the word 'royal' attached to it, and his patronages, particularly the military ones. I think he and Meghan were counting on all those things to enable them to springboard into the life they'd planned as global philanthropists and important people who could leverage their names and titles to have real influence. The deal the RF family cut them though and the timing of the pandemic put paid to all of that and, in addition, they had to come up with a way to make lots of money fast. They needed the sort of home that befitted their status, and they needed round-the-clock security, which surely costs a fortune. And with them both feeling angry and slighted and out-manoevred do you think they care that they're damaging the very institution and the very people they blame for putting them in that position? I don't.
So is all of this Meghan's fault? I think Meghan has enabled and encouraged Harry to do what he's doing and I think while she's conspicuous for her silence over the past week or two, she's 100% behind everything he's said and done. Plus, I think she's the one with the huge ambition for them to be movers and shakers on the world stage, people who are there at the tables where big decisions are made. Those Commonwealth roles he talked about? I reckon that's her. I honestly think he'd have been happy to potter off to Botswana and work in conservation before she came along. I think there are no limits to her ambition and if the RF think they can placate the pair of them with a muttered apology in private, they can think again.