The Kochs like people like Scott Walker because they're basically schmucks who have never been successful in business or made any serious money so they're in awe of people like the Kochs and Sheldon Adelson. Donald Trump doesn't have anything to prove, he isn't impressed by anyone's wealth but his own and no one can afford to buy him off. And he seems to have the "been there, done that" view of business of someone who has spent their life dealmaking, as opposed to all the Republicans who were poli sci/law school graduates, never worked anywhere besides government/nonprofit/law and think the "private sector" is some magical job-creating wonderland that is perfectly efficient and innovative and never does anything wrong or bad.
The Koch brothers have created a company with 60,000 people without the help of government. They have created non-profits and have given millions to charity. They aren't on television every two seconds.
By contrast, Donald Trump is where he is today because of the help of government. His only venture into politics was considering presidential runs in 2000 & 2012, and wasting money on having "investigators" try and find Obama's birth certificate.
Trump hates the free market. He supports the government getting involved in health care, taxing the very wealthy, and in taking people's private property. That's why the Koch's and every American who loves capitalism, loves freedom, and loves America won't be supporting Donald Trump and his treasonous presidential bid.