Here's a taste:
Why were charities Mr. Abramoff’s go-to vehicles as he sought to transfer funds covertly through Washington’s corridors of power? The primary attraction was their opacity: their ability to raise money in any amount, without limit, from any individual or entity anywhere in the world without disclosing the contributors to anyone.
This makes good sense for honest charities helping people in need. But Mr. Abramoff took advantage of this situation to circumvent campaign finance laws and Congressional ethics rules and provide illicit benefits to powerful politicians.