Why did the Hamilton Watch Company move its manufacturing operations from Pennsylvania, USA, to Switzerland, in 1969?

Hamilton acquired the Swiss company Buren in 1966. Three years later it closed its US operations because of lower labour and manufacturing costs:

In 1966, the brand acquired the Buren Watch Company of Switzerland, including their factories and technologies likeBuren's innovative micro-rotor. The two companies mixed components for the next three years before Hamilton finally ended its seventy-seven-year history of American manufacturing and routed all production to Switzerland. This shift - made in part due to the low comparative cost of labor and manufacturing - proved well-timed.

https://windupwatchshop.com/en-au/blogs/chronicle/a-history-and-guide-to-hamilton

This website doesn't mention Buren. It was Hamilton's diversification and the associated losses, as well as the poor quality of watches, which caused the closure of the US watch division. The author blames Jacob Hain:

In 1961, the HWC bought Standard Time Corporation, A Virgin Islands wholly owned subsidiary company. This division was making the Vantage products at a greatly reduced price and quality for the HWC's lower end products. The obvious ploy was to compete with the Swiss as they had lower labor costs, and it was hard for the HWC to compete. The HWC grew into a large conglomerate; it was more than just a watch company. The HWC became involved in Wallace Silversmiths, Puritan Fireplace Furnishings, Industrial products, elapsed time indicators, gauges, battery operated timing devices, photo etched products in electrical components for computers and aerospace ... They were all over the place and they were not focused on what they did best, watches. In the 1964 Annual Report it states, "In May the Canadian plastics business was sold and a contract for the sale of the Puritan Fireplace Furnishings division was executed in January 1965, neither of these businesses was compatible with our other operations nor did they promised sufficient profit in the foreseeable future to warrant continuing our investment in them." The key words here, "not compatible with our other operations."

The demise could either be attributed to Art Sinkler and his expansions outside of the watch making arena, the Swiss competition or probably was more likely due to a fellow named Jacob Hain, through his Penn Square Mutual Fund (Bush Terminal out of Reading, PA), who bought a large chunk of the HWC. His company owned 30% of the stock in 1961 which they started buying two years prior, and by December 1963, his company owned nearly 54% of the common stock ... When the HWC acquired Standard Time in 1961 for its inexpensive Vantage line of watches. This was contrary to the HWC longstanding practice of elevating quality over quantity. Through Sinkler's leadership, the quality of Hamilton watches in the early 60's took a steep dive: dials were now for the most part embossed and made of brass, not of sterling with solid gold numerals; most of the cases were made in stainless steel and rolled gold plate, micro plated, not gold filled; and most the movements were imported from Switzerland and marked "Hamilton" ...

In closing, the demise was either through the expansions of Art Sinkler (20% of the blame in my opinion) or Jacob Hain's Penn Square-Bush Terminal (80% of the blame in my opinion). This is 100% my opinion from the materials I have read. I also feel that if Hamilton just made watches of high quality, they could have survived as just a watch company as many of the other major American watch brands were out of business.

https://www.vintagehamilton.com/articles/the-demise-of-the-hamilton-watch-company-in-lancaster-pa-and-the-rise-of-the-swiss-owned-hamilton-watch-company