China wanted to distance itself from the USSR, and the US wanted to separate them as well. Thus, normalization of relations with China was seen as a good thing, even if it meant recognizing China in place of Taiwan.
The Beijing-Washington Back-Channel and Henry Kissinger’s Secret Trip to China
https://nsarchive2.gwu.edu/NSAEBB/NSAEBB66/
Kissinger flanked Russia and ended the war
By visiting China, he ended the need for the war in Vietnam. China trumped Russia.