The part you find difficult to grasp is that people generally only have so much free cash to give to worthwhile causes annually.
In aviation historical circles the Vulcan has take away quite a bit of that free cash year on year, as people do find it a worthwhile cause.
People are more than welcome to donate to whoever they wish, but generally donations to aviation related good causes in the UK have fallen while the vulcan has been flying.
But this is precisely the point. You are arguing that the Vulcan be grounded in favour of other projects on the grounds that the public clearly prefer the Vulcan to those other projects.