LIHOP is an acronym which began to be seen following the surreal events of September 11, 2001 (“9/11”). Some believed about 9/11 that “they Let It Happen On Purpose” (LIHOP).
Think of President Franklin Delano Roosevelt (FDR) knowing full well that the Japanese were about to attack Pearl Harbor in December 1941 and letting it happen on purpose because it would further his overall plans. (Background: Hoover’s Secret History, Ersjdamoo’s Blog, November 16, 2016.)
In a posthumously published book, former President Herbert Hoover alleges that the FDR Administration knew an attack was imminent and yet failed to warn those based at Pearl Harbor. 
This theme of LIHOP appears in a book by the late Shelby Foote. You may remember Foote from the Ken Burns documentary on the Civil War, where Foote was prominently featured as an authority on the subject. Foote suggests that President Abraham Lincoln cunningly maneuvered the Fort Sumter crisis so that the April 12, 1861 bombardment would be likely. “Lincoln,” writes Foote, “had maneuvered them [the Rebs] into the position of having either to back down on their threats or else to fire the first shot of the war… Lincoln soon had cause to believe he had judged correctly. Sumter did indeed unite and electrify the North.” 
In Charleston, South Carolina, Reb “fire eater” Roger Pryor had proclaimed, “Strike a blow!” shortly before April 12th. The southern crowd listening was delighted. “So would Lincoln have been if he had heard him, for by now he saw Sumter as the answer to his need for uniting the North.” 
——- Sources ——-
 “Pearl Harbor Reconsidered”, Ersjdamoo’s Blog, December 4, 2016. https://ersjdamoo.wordpress.com/2016/12/04/pearl-harbor-reconsidered/
 The Civil War, Volume 1 (chapter 1), by Shelby Foote. New York: Vintage Books, 1986.