Billionaire conservative donor David Koch died Friday at the age of 79 from prostate cancer. David Koch — who was worth some $42 billion — and his brother Charles poured massive amounts of money into funding climate change denial through conservative think tanks and politicians. The Koch brothers founded the political advocacy group Americans for Prosperity in 2004, which is credited with turning the “tea party” into a full-fledged political movement. They also backed “right-to-work” efforts, which aim to weaken labor rights and quash union membership. The brothers made their fortune running Koch Industries, the second-largest privately held company in the United States. We speak with the business journalist Christopher Leonard, who just last week published a major new book examining the business dealings of the Koch brothers. It’s titled “Kochland: The Secret History of Koch Industries and Corporate Power in America.”