Manufacturing as a percentage of gdp had been flat since the late 1940s. Automation has eliminated a lot of jobs.

"Manufacturing's share of real GDP has been fairly constant since the 1940s, ranging from 11.3 percent to 13.6 percent. It sat at 11.7 percent in 2015."

https://www.stlouisfed.org/on-the-economy/2017/april/us-manu...