Philanthropy is not the only metric when considering if someone is a good person.
And admittedly I have no first hand knowledge into any of these people, only information provided from books, interviews and biographies so my impression of these people may not be accurate at all.
It would paint a more complete picture of who they are. Better yet, a personal diary or collection of letters (an autobiography gives too much room for the author to lie).
It can also be purely rehabilitation for the image, as in the case of Alfred Nobel and his prize. How many people know about the Nobel Prizes? How many know how Nobel made his money?
> Musk
Musk participates in disaster relief, education and The Giving Pledge.[1]
> Ellison
Ellison participates in The Giving Pledge. [2]
> Gates
Really?
> Bezos
Bezos supports the Dreamers (after some pressure, yes). [3]
> Jobs
Jobs shut down Apple's philanthropy department when we returned to Apple in 1997.[4]
[1]: http://www.borgenmagazine.com/elon-musks-humanitarian-effort... [2]: https://associationsnow.com/2014/09/larry-ellison-teaches-na... [3]: https://www.inc.com/minda-zetlin/jeff-bezos-first-big-charit... [4]: https://www.theatlantic.com/technology/archive/2011/08/yes-y...