The working class was making a living wage doing, for the most part, manual unskilled job (pull a lever on a converyor belt or making US flags.
I'd like to know where you got the idea that the working class was doing mostly manual unskilled jobs.
Because I was in the middle class doing manual unskilled work (soldering electronics) 26 years ago. Because that is what I saw predominantly everywhere I went. Yeah, you had a factory that manufactured and repaired electric motors. For each one of "you" there were a dozen of "others" truly doing unskilled jobs.
Jesus, look at all those people that used to work in the auto industry. Sure, there were truly skilled laborers, but the lot was just put thing A in mold B, yell "clear" and pull the lever. The garment industry? Unskilled by modern standards. Assembly of electronics? The bulk of it is unskilled by modern standards.
Look at the work done by FoxConn workers in China. Yeah, they are assembling your fucking awesome, newest iButtPlug electro-trinket, but those workers are unskilled. They simply pick part A and B from conveyor belt and put them together in a bucket in another conveyor belt.
Those are the type of manufacturing jobs that were predominant here, that were uber-sophisticated by the standards of the 50's and 60's when Europe and Japan were recovering from the ashes, China and India were completed fucked, Latin America was fucked and incompetent (hasn't changed much) and 2/3 of the planet was living in some weird state mixing stages from the Neolithic, Iron Age and Feudalism with a bit here and there from the Industrial Age circa 1800's.
Things changed, and those uber-sophisticated jobs no longer count as skilled. The rest of the planet did some catching up, and what counted as skilled now counts as menial.
Time to deal with it.