Is he willing to destroy it because he doesn't actually care about the people it helps?
No idea; I'm not terribly interested in trying to divine what goes on in Harry's mind (if anything). I don't think he's a strategic long term thinker, if that helps. I suspect he struggles without the 'men in grey suits' to arrange every single aspect of his life for him.
I think Sentebale was probably set up, first and foremost, to give Harry something to do and to keep him away from the posh party circuit in London, because there was a period of time where he was going down a bad road. It appears to have done that to an extent and helped lots of people along the way, so kudos to the grey suits for that. But unmoored from their steadying hand, it took five years for it all to start falling apart. And of course, the development and aid worlds have changed a lot in the past few decades and there's been some extremely intelligent and experienced women on these threads who know those worlds and have explained it all very well.
The mass resignation can be seen in one of two ways - either as a tactic to try to force SC out, which is bloody high stakes, or because the resignees know that there exists documentation which might paint their stewardship of the charity in a less than favourable light. I assumed the latter, although that's from my experience of private companies and organisations. I don't know the charity world much at all.
Anyway I'm so pleased that there are some fellow Behavior Panel fans here! They are the only YouTube speech & body language analysts that I take seriously because they've got proper academic training and real world experience behind them. I've had a couple of clients who've done work with Mark Bowden and have only ever heard really excellent things about him.
Their analysis of the Netflix doc Harry & Meghan is well worth the time.