The Donors Trust is a "donor advised fund", meaning that it has special status under the US tax system. People who give money receive generous tax relief and can retain greater anonymity than if they had used their own charitable foundations because, technically, they do not control how Donors spends the cash.
This is outrageous. I really think Congress can fix this this by requiring disclosure of the companies who contribute to these causes, without running afoul of First Amendment concerns. It remains to be seen whether there is enough political will to do this though.