If the employer of a “sweatshop job” is not coercing or lying to its employees, then I have a hard time faulting the employer directly. We may still want systemic change to create more options and more equity for employees, but the “sweatshop” (that pays more than alternatives and which employees freely choose) is not the villain in this story.
I wonder if the biggest reason he didn't hate his job was the gratitude from other people. One of my first jobs was stocking shelves on the graveyard shift at a grocery store, and the 1 hour or so before the store closed I would occasionally help shoppers find things, help take heavy things to their car, or help them reach items high on the shelf. A sincere thank you always made the 7h of mind numbing stocking go a lot faster.
As I can't find a reference, you can treat this as anecdotal - but there was a radio story about 2 fifteen year old siblings who'd both 'taken up sweatshop work'. One was stitching trainers, one was doing embroidery - for very low wages.
Initial 'outrage at child-labour' was confused slightly when they both said they were very happy, as they'd previously been working on their parents farm - and their sweatshop labour had allowed them to contribute towards a tractor for their village (replacing the labour of a whole load of children) - and for the first time they had some personal savings.
If you want to go deeper on this subject I highly recommend reading Factfulness.
Outlawing sweatshops effectively creates a wage / work conditions cartel.
Where I live, I know some people who work/have worked in the local fulfillment center, and say that few people manage to transition to full-time/permanent, they seem to find ways to fire/lay off people before they get there, the workforce is constantly turning over.
Different locations may be different though.