Unions had early wins that mostly either didn't go anywhere, or the companies worked around. The real win that normalized it was for capitalistic reasons, when Henry Ford shortened the workday/week because he wanted his workers to buy (and have reason to buy) his cars. Combined with other changes, he figured he'd retain workers better and reduce mistakes from fatigue, and when he remained competitive others followed suit.
This is a common fable and it doesn't make sense. He increased wages to decrease turnover. It's honestly crazy that Fordist propaganda is still circulating today. The dude was a pro-Nazi freak.
Him being a Nazi sympathizer has nothing to do with this. Also you verified one thing I said and didn't refute the point of my comment about the workday/week.
