They aren't always what you would consider a "robot" but rather a process. A CNC machine can do in 5 minutes what it would take a worker on a manual lathe/endmill hours to make. It still takes a technician to load a casting into a machine and do quality checks after, but you can teach most people to do this in a day or less, while manual machining requires skilled tradesmen.

There was a steel mill in PA that made a lot of the steel used in WW2 production, they were running thousands of people per shift over three shifts, and this was extremely hard and backbreaking work. There were cities built around these steel mills. A modern steel production facility where I live might have 100-150 or so employees on a shift.

It's the same for auto manufacturing. Thousands turned into hundreds. Companies got rid of skilled laborers because they can't find them anymore.