Which business and union are you talking about specifically?
As unions usually live on either/and employee dues and government grants, making sure both the company and the industry overall is doing well is in their best interest, as otherwise the union will certainly not be alive.
So would be useful to see an example of a union NOT wanting good for the company/industry as that would be an outlier compared the the rest of them.
Management has no reason to oppose changes that cost them nothing with or without a union. In an industry with thin margins, anything that does cost them money puts them out of business. Meanwhile a union that can't achieve meaningful concessions is collecting dues for no benefit, requiring the company to pay more to retain talent and thereby putting them out of business just by existing.
This is a very simplified way of thinking about it. Costco manages to be profitable while paying more than the average to retail workers in an industry with thin margins. Whole Foods managed this too until it was acquired.
It's funny how the US is often presented hyper innovative, and economically dynamic, while at the same time it is claimed that basic issues like universal health care and workers rights - problems that are solved in many other developed countries - are intractable in the US because of "thin margins" or "the deficit".
Costco operates in the same market conditions Walmart. It's just that their revenue to employee over twice as high, so they can sustainably pay a small number of high-quality workers more rather than a large number of lower-quality workers.
Pro-labor operates under the false assumption that employing a small number of well-paid workers is better for society than employing a large number of lower paid workers. Let's say Walmart could afford to pay a "living wage" by replacing their shelves with pallets, laying off most of their shelvers, and redistributing their wages to the other employees. Would that really be any better?
