Actually, Gingrich insulted Reagan repeatedly in the 1980s

As a new member of Congress in the Reagan years — and I was an assistant secretary of state — Mr. Gingrich voted with the president regularly, but equally often spewed insulting rhetoric at Reagan, his top aides, and his policies to defeat Communism. Gingrich was voluble and certain in predicting that Reagan’s policies would fail, and in all of this he was dead wrong…

The best examples come from a famous floor statement Gingrich made on March 21, 1986. This was right in the middle of the fight over funding for the Nicaraguan contras; the money had been cut off by Congress in 1985, though Reagan got $100 million for this cause in 1986. Here is Gingrich: “Measured against the scale and momentum of the Soviet empire’s challenge, the Reagan administration has failed, is failing, and without a dramatic change in strategy will continue to fail. . . . President Reagan is clearly failing.” Why? This was due partly to “his administration’s weak policies, which are inadequate and will ultimately fail”; partly to CIA, State, and Defense, which “have no strategies to defeat the empire.” But of course “the burden of this failure frankly must be placed first on President Reagan.” Our efforts against the Communists in the Third World were “pathetically incompetent,” so those anti-Communist members of Congress who questioned the $100 million Reagan sought for the Nicaraguan “contra” rebels “are fundamentally right.” Such was Gingrich’s faith in President Reagan that in 1985, he called Reagan’s meeting with Soviet leader Mikhail Gorbachev “the most dangerous summit for the West since Adolf Hitler met with Neville Chamberlain in 1938 in Munich.”