In "The Gorsuch Triumph", Ramesh Ponnuru states that Robert Bork was rejected by the Senate in 1987 "for being too conservative". This is a gross oversimplification, and even a misstatement of, Bork's confirmation problems.
Bork's view was that the Constitution restricted the ability of government to limit our freedoms only to the extent of liberties specifically spelled out in the Constititution. This is the exact opposite of what our Founders intended. The Founders intended that "We the People" were only giving government the powers specifically outlined in the Constitution, with all other powers being reserved to the people. Bork's endorsement of excessive power for the federal government, well beyond that intended by the Founders, can hardly be called "conservative" in any meaningful sense of the word.
But Bork had more problems than this. He came across as aloof and unapproachable, turning off even many of his supporters. As Senator Howell Heflin commented, "He's too professorial".
As documented in Ethan Bronner's "Battle for Justice: How the Bork Nomination Shook America", Bork waffled over key issues during his confirmation hearing, repeatedly flip-flopping back and forth. This made him look hopelessly opportunistic, and called his character into question. Bronner says that Bork "modified views he had held strongly and repeated widely for two decades". His repeated waffling earned him "the contempt of some fervent admirers".
Ponnuru states that Bork got "burned for his candor". To the contrary, Bork lost because he was unable to communicate his beliefs in an understandable way, despite Committee Chairman Biden's bending over backwards to give him a fair hearing. Consequently, the Senate rightly concluded that he would not make a good Supreme Court justice.