Which injustice exactly? It is just a basic corollary of private property.
>Billionaires like Musk got to where they are because they started with so much wealth to begin with, not because of skill or intelligence.
Elon Musk, whatever you think of the person. Has created jobs for tens of thousands of people and guaranteed the US leadership in space. Elon Musks wealth is in his companies. Even if you do not like Musk, Tesla and SpaceX existing are beneficial, at least to the tens of thousands of people who are working for these companies. I see no injustice at all.
Of course the person in the article is an enormous hypocrite, since she choose to become a multimillionaire, based on her "injust" inheritance. Almost nobody will receive an inheritance as great as hers after giving 92% away.