Big "philanthropy" isn't a new concept. It's more than a 100 years old and was created by the "robber barons" of the gilded age to shelter their money from taxes and keep the wealth under family control for generations. An added benefit of these family charities is great PR. The most famous beneficiary of the charity PR is john d rockefeller whose reputation improved immensely after setting up his family charities. Rockefeller revolutionized the modern use of a PR team to burnish one's image through radio, tv, etc. A more recent example of this is bill gates who used charity and pr teams to shift public perception of him from a greedy tech monopolistic to a charitable philanthropist. Bezos is just following in a long line of extremely wealthy people.

Whether it is good for society to immense wealth controlled by family trusts/chariities or whether the wealth should be taxed and used for public purposes is something people can debate for an eternity.