Television sponsors. Follow the money. Always follow the money.
http://www.nj.com/golf/index.ssf/2015/08/donald_trump_comes_to_the_barc.html
Given what Trump has done for golf and what the the golf fans think of Trump this could be one of the dumb ass moves of the year. Read that story. And think of the GOPe types that run the PGA. Talk about going bassackwards.