It was Bush Senior, Clinton (with PNTR), Bush Junior. The story of why the US thought PNTR was a good move is long, and has to do with the events of 1989. Also... Jiang Zemin and Hu Jintao were both very different from who we have today. China was not necessarily friendly, but they thought there was a good chance of them becoming friendly, especially if their market opened up. For several years after Tiananmen, the Democrats in Congress actually wanted sanctions against the PRC, but it kept getting vetoed, so as not to torpedo the chance.