I think it really comes down to the following:

In the 1970s, we needed ally in Asia to backstop our failures in Vietnam, and Nixon going to China was an apt opportunity to take advantage of the so called Sino-Soviet split[0], as Soviet and Chinese relations had been deteriorating since Stalin[1][2].

At the same time, Nixon was facing what would become one of the broader pain points of the 1970s that Nixon had to deal with, which due to both increased domestic spending and the war in Vietnam, the US was entering a situation that was economically becoming increasingly fragile (and culminated with the closing of the "gold window"), to quote A research paper by Scott W. Ohlmacher at the University of Delaware, THE DISSOLUTION OF THE BRETTON WOODS SYSTEM
EVIDENCE FROM THE NIXON TAPES:

>In August 1971, the Nixon administration faced an international monetary

>crisis. The Bretton Woods system, established in 1945, was crumbling. Under the

>Bretton Woods system, the US dollar was pegged to the value of gold at the price of

>$35 [USD] per ounce. Most of the world's other currencies were then subject to fixed

>exchange rates with respect to the dollar. Growing concerns over rising current*

>account...and government deficits in the United States drove

>investors away from the dollar and encouraged purchases of gold. Gold outflows, as

>depicted in Table 3, began in the second quarter of 1970 and continued in earnest until

>the fourth quarter of 1971.

>Nixon was very much aware of the fact that the US dollar was overvalued,

>and as gold outflows continued, it became apparent that the United States would not

>have enough reserves to maintain convertibility.[3]

Given this, Nixon was smart to pursue softening relations with China, opening them up to new markets (which the economy was increasing going to need, which become clear at this point his presidency), between that, and Nixon softening relationships with the Soviets (so called `Détente`[4]) to, what I believe was to largely avoid a very costly arms race, which Ronald Reagan was happy to involve the US a decade later.

Fast forward a bit, and a rapidly White Collar emerging workforce with a strong pro business administration in the 1980s, and you have a recipe of Corporations who want to take advantage of this new trade partner (much of Nixon's and later administrations negotiations came to fruition in the Reagan years) to lessen the cost of production in manufacturing of goods, and saw new market opportunities, in particular for large domestic brands, such as Coca Cola, General Foods, And even AT&T[5].

This calumniated with China joining the WTO in 2001 and a fairly liberal expansion of US trade activity there after (US exports to China increased by 341 percent[6]), again, aligning incentives in such a way that kept these relationships alive.

Only since 2009 and in particularly the mid 2010s did the US - and I think many other countries in the EU - started to take notice of issues with their relationship with China, and the actual affects of all these decades of relentless openness with a country that did not always respond in kind, as we later found that they were stealing industrial secrets, saw increased activity from the Chinese intelligence services, and staunch protectionism[7][8][9][10][11][12], and ongoing human rights abuses[13]

[0]: https://en.wikipedia.org/wiki/Sino-Soviet_split#Origins

[1]: http://www3.nccu.edu.tw/~lorenzo/Goh%20Soviet%20Card%20Openi...

[2]: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.18...

[3]: https://udspace.udel.edu/bitstream/handle/19716/4275/Ohlmach...

[4]: https://en.wikipedia.org/wiki/D%C3%A9tente

[5]: https://journals.sagepub.com/doi/full/10.1177/18681026100390...

[6]: https://journals.sagepub.com/doi/full/10.1177/18681026100390...

[7]: https://www.theguardian.com/world/2020/feb/06/china-technolo...

[8]: https://thediplomat.com/2020/05/why-chinas-technology-theft-...

[9]: https://ge.usembassy.gov/how-the-chinese-communist-party-ste...

[10]: https://www.csis.org/programs/technology-policy-program/surv...

[11]: https://thediplomat.com/2018/05/why-china-wont-abandon-its-c...

[12]: https://www.washingtonpost.com/world/us-companies-feel-unwel...

[13]: https://www.amnesty.org/en/countries/asia-and-the-pacific/ch...