Discussing this with you is slightly exasperating. You are the one who posted a quote claiming Dumfries House was a Save Britain Heritage Campaign where the quote said the house would belong to Save Britain Heritage. So clearly that was the initial plan, or the quote you posted was wrong?
Right back at you, to be honest - you are so utterly determined to see this as something dodgy, is that it? And you so fond of preaching critical thinking - consideration of the timeline would help here, rather than just approaching this with hindsight.
This quote “preservationists…organised a campaign intending to buy the house and hold it in trust under the Save Britain's Heritage organisation” describes the situation before Prince Charles’ involvement. At that point in time, when the house and its contents had literally been put up for sale with Saville’s and Christies, this was the plan - raise the funds to buy the house and for Save Britain’s Heritage to hold it in trust. At the 11th hour Prince Charles became involved and not only was he able to raise the funds to buy the property from the family, but he was also able to come up with a different plan for its future use.
So the quote isn’t wrong, but rather correctly described the situation as it was when the house was put up for sale. At that stage the campaign was headed by Save Britain’s Heritage. When Prince Charles came on board the plan changed. Since it resulted in the house and contents being saved, restored, opened to the public and used for an educational facility, I can’t imagine anyone but you has a problem with that.