I apologize if the question seems vague, but it seems to me that an unusual number of manufacturing firms were bought out, went bankrupt, or otherwise ceased to be in both the UK and US during this period. Is there some particular economic reason for this?
In terms of manufacturing specifically, in a way, the companies started going out of business because they got too efficient and a little lazy. Production outpaced demand and companies were having trouble keeping their businesses going once the recession hit and spending went down. So companies had to shut down or otherwise merge in response.
In addition, globalization allowed consumers access to cheaper goods from other countries. This combined with a lack of growth and innovation in American manufacturing led to a slow decline starting in the 50s but really ramping up in the 70s. The Minneapolis Fed article below suggests a causal link between lack of competition leading to a decline in innovation in the Rust Belt and foreign competition created a sharp decline in the industry, which leveled off in the 80s once the industry adapted.
The 60s and 70s saw several energy sector crises related to petroleum. These in turn led to market collapses and the stock prices of many companies falling. As a result, many companies went bankrupt during this period.
https://www.theguardian.com/environment/2011/mar/03/1970s-oil-price-shock
Deregulation was one of the tools used to combat this downward spiral in the United States, starting with the Carter administration but ramped up during Reagan's tenure. It's possible this allowed for companies being bought out or otherwise going through mergers that couldn't have in the past. But on the other side, we ended up with fewer manufacturing companies.