I think that the extreme dishonesty of the press surprised Trump. He was used to the business world where people try to get a good deal, but not by cheating which would invalidate a contract. Of course he already knew that politicians cheat.
History is replete with honest people who have been blindsided by the corrupt. Ulysses S Grant, was victimized by people he trusted. The honorable people who served under him in the Civil War would have never stooped that low, so he never expected it. Big fortunes were made during reconstruction by "carpet baggers" and railroad tycoons. It happened right under his nose.
Finally, when he was living in New York, his business partner stole all his money and left the country. The great Civil War general, the man who actually admired Robert E lee, was in poverty.
Mark Twain had been telling Grant to write the history of his life and finally Grant decided to do so because the could provide for his family that way. He was dying of cancer.
Twain was right, it provided for his family.