I recalled this story [0] where the Koch brothers said they would organize $1 billion to conservative groups for the 2016 election.
[0] https://www.cbsnews.com/news/koch-brothers-network-will-spen...
[0] https://www.cbsnews.com/news/koch-brothers-network-will-spen...
As the article notes, Trump (who was not Koch-backed) won with very little spending compared to his big-money backed conventional GOP opponents. They decided to step back and spend less in 2016 as a result, since they didn’t support either Trump or Hillary.