Because they already own those assets and don't want anyone else to have them. The perception of wealth is always relative so if I can't make any more to maintain my status I must ensure that others can't get what I have.
Not sure if the causality there is the right way around, I would suggest that because they have these beliefs they are allowed to amass that wealth. Oracle is a CIA spin-off (1977), they even kept the code name. The CIA works closely with Mossad. The 'abolish all billionaires' plan is encouraged precisely because it will be ineffective - they're assets of the state secret police and good luck abolishing that.
