David Koch, a billionaire libertarian who supported conservative causes and campaigns, died at the age of 79, according to an announcement from his family on Friday.

Why it matters: Koch and his brother Charles built a massively influential network of donors that backed politicians who supported economically conservative policies, though he stepped away from his work last year due to his deteriorating health. The Koch network has faced criticism from President Trump throughout his tenure — notably due to breaks on immigration and trade — and said it would not support his re-election efforts earlier this year.

Go deeper: The Koch network is open to backing Democrats in 2020