The establishment is doing it. He’s their slave boy.
Trump was too cheap/lazy to bother spending the money to build a grassroots org.
Trump’s failure if he fails to get 1237 delegates will be his and his alone.
So far he has benefited from the process getting more than the 37% of the delegates in spite of getting only 37% of the votes.
Trump is screwing his supporters by not investing in an org that would put them in position to win.
Perhaps that was part of his phone call with Clinton?