Activists always want to take credit, but it's the engineers and scientists who actually did the thing that changed the pattern that had lasted for 10,000 years. Unions are just one particular way of structuring one side of a human conflict that is as old as civilization and as inherent as gravity.
[1] https://en.wikipedia.org/wiki/Triangle_Shirtwaist_Factory_fi...
For thousands of years those bad conditions reigned. For thousands of years, 'organized labor' changed nothing. Then technology changed, and suddenly 'organized labor' became able to offer all these wonderful things. Does it sounds like 'organized labor' can take credit for all that? That they just happened to succeed in the decades after industrial technology took off?
The timeline clearly indicates technology, which increased productivity across the board, as the root cause.