“In 1979, after a thoroughgoing reinvestigation, the House Select Committee on Assassinations officially concluded that Kennedy “was probably assassinated as a result of a conspiracy.” But such findings seemed not to penetrate. “In view of the overwhelming evidence that Oswald could not have acted alone (if he acted at all), the most remarkable feature of the assassination is not the abundance of conspiracy theories,” Christopher Lasch, the historian and social critic, remarked in Harper’s, “but the rejection of a conspiracy theory by the ‘best and brightest.’” For complex reasons of history, psychology, and politics, within the American Establishment it remained inadvisable to speak of conspiracy unless you did not mind being labeled a kook”
https://nymag.com/intelligencer/article/jfk-assassination-documents-national-archives.html