Distributed in this sense isn’t a past-tense transitive verb with “wealth” being the object of the verb. It is used as an adjective describing the current arrangement or division of wealth. You can say “They distributed the widgets, leading to how they are now distributed.” Think in terms of statistical distribution.
So to change how wealth is currently distributed, it must be re-distributed.
Interesting point. The initial distribution is the natural flow of money through the marketplace. The redistribution is the corrected flow.
Of course, the whole concept of “corrected flow” is absolutely destructive of freedom and prosperity... but that is probably where the term comes from.