I'd argue that it doesn't actually benefit them now since they have more access to comfort than they could ever conceivably consume in their lifetime but I do absolutely agree that they think it benefits them because people who have accumulated wealth to that degree are highly fixated on making the number go up.

A less just, less stable society is far more likely to demonize and destroy billionaires. If you have such a high level of wealth the most rational action is charitability to insure the wealth of people who surround you to prevent instability and lower the chances you'll be the victim of a crime carried out due to desperation.