[Digory]

The sentence from the article is:

"While the total amount the Greens have made in charitable contributions has been kept private, former Oral Roberts University president Dr. Mark Rutland may have worded it best when he described the family as “kingdom givers”.

It doesn't link to the Forbes article's definition. Without more, I'd read that sentence to say "Kingdom givers" is a descriptor of the total amounts given by the Greens -- we don't know the amount, but they give kingdoms.

As I explained above, "Kingdom" is unrelated to the size of the gift, as made clear from the quote you cited.