Invictus has always been Harry's lifeline to universal praise and good press. With it being held in the UK, it could be his gateway back into being a working royal. We absolutely know that the royals - particularly William - will be vilified if they don't "support the veterans" - irrespective of what they do for the military all the other years when Invictus hasn't rolled into town. So it's no big sacrifice, and actually good PR for Charles to support it, and it's a shoe in win for Harry - and perhaps his last chance to get back into the royal fold before William becomes king and shuts off all avenues. All he has to do is behave himself next year and not overshadow Charles's tours and other major engagements with his own Temu royal activities like faux tours. Charles will want this because he's both a narcissist who doesn't like being overshadowed, and very aware he has limited time left to make his mark as king. And I don't think he cares about the impact on William, unfortunately.
Is Harry after money or becoming a working royal again? I think he will take either, but he will persist in wanting the latter on the HIHO basis, as I simply don't see Meghan returning or the children coming back either. Perhaps she'll capitulate if Charles promises to leave them one of the major, privately owned properties, like Highgrove, that Meghan can take over and impose her brand onto. Perhaps Charles is dangling some attractive carrots in their faces to get compliance?
Will Harry and Meghan comply? Like | said, they are scorpions, and I fear froggy Charles will come a cropper. I think their response to anything the king and his heir does is Pavlovian and they can't help themselves but seek to compete with them. And they have the press all too willing to facilitate this - the continual jabs at William and Catherine for no good reason being demonstrative of the current dynamic. All Meghan will need to do to knock Charles off the headlines is walk around a carpark in some wrinkled monstrosity; and this will especially be the case if they have actually gone quiet for a period of time and curiosity as to what they have been up to ramps up. One thing these last few months has shown is that over-exposure to Meghan's "brand" has simply resulted in ridicule and ennui. She's better off staying mysterious.
At the moment, I think there's probably a lot of brinksmanship at play, given the uncertainty over Charles's health and the Sussexes rather precarious position, which makes them far more dangerous than if they'd managed to secure a solid and successful career for themselves outside the RF.