Can anyone explain how
£1bn appears like Magic to help repair an admittedly beautiful Cathedral, whilst
The Magic just "isn't there" when it comes to human need.
Was not the Nôtre Dame Cathedral also made by human beings?

it's because many human beings who accumulate wealth prefer to reserve it for their own, and they consider Notre Dame cathedral to be one of their own.

humans often aren't very good at empathy for large numbers of other humans; they become a collective "humanity" that becomes more abstract than a building. Our shared cultural heritage becomes more important than the people who create it.

I think Snailquake and Arbieroo have described the answers succinctly.

I think they find it easier to deal with a single icon than with the never ending bottomless pit of looking after the world’s population. It’s much more tractable.

that's another good explanation

Indeed.

although, numerous people have calculated that human need is a problem of uneven distribution of funds, not a lack of them. Money being an abstract concept, more is always being made, so there is no bottomless pit.

that takes no account of inflation.

most of what's called inflation is just another artefact of the unequal wealth distribution system. The only real component of inflation would be people's expectations - eg of what medical science can do (whether NHS or otherwise) or from computational gadgets etc as opposed to mere subsistence living.

also, every time someone calculates it anew, they reach the same conclusion for that point in time, with that world population and currency levels.