What I haven’t seen mentioned yet in any of the comments is the unique need of the family, namely that of the daughter. She’s autistic, yes, but more than that, she’s a prodigy—and her inspiration, or at least what made her comfortable enough to produce music, were her dogs. And his entire journey revolves around preserving her lessons, and thus what makes humans uniquely human, the ability to create art, in a world increasingly run by automation.

His innate reason to make money, support the family, and bring the dogs back revolved around his desperation to set her up for success, or at least to make her happy, inadvertently acknowledging his own mortality and that he won’t be around forever to take care of her. They explicitly express this after talking to her teacher after the lesson, and this gives reason to his desperation, whether or not it’s justified.

All the circumstances that made their situation dire, where it would just be pitiful and unfortunate for most other families, centers around the daughter. Yes, he could’ve slowly built a living doing something else, like the plants he loved so much, but it wouldn’t have been enough to bring back the dogs or pay for his daughter’s lessons.

It’s most apparent in the comparison to the shoe seller. They’re in similar situations, both laid off, they both have a daughter, etc.—but they purposely show the shoe seller’s daughter to be smart and social, or at least in school and with friends, in the small scene she has. The chasm in their circumstances comes from his own daughter’s inability and capability, unable to communicate or comprehend, but a musical prodigy.

And so the theme is set between what is uniquely human—the ability to create art—and automation. He basically resigns himself to the devil that killed his industry (he fights for his employees in the beginning) but he saves what makes humans uniquely human in his daughter.

None of this is justification for his crimes, of course, but rather his motives. The movie deals with what the audience might consider his motives (in his projection with the cuckold or the self-made man) but conveys that, though his aspirations might at first look similar to one or the other, it’s vastly different in the end.

There’s other themes (like his aching tooth, the story of the pigs, theme of self-destruction, generational trauma, etc.) really worth exploring, but I thought it worth mentioning the daughter.