I think you’re missing the point. It’s that they built it to begin with. And it’s not always enclosed. Stadiums exist all over that aren’t air conditioned and don’t close. It’s the level of effort to overcome the heat. Yet we still can’t air condition damn Amazon warehouses or UPS trucks. Both of those have had folks pass out from heat.
Oh we can, those corporations choose not to. The stadium owner has an incentive to ac the stadium since a more pleasant temperature is likely to attract and please most customers. Amazon is working with a captured market and people who, alone and individually, don’t have any power. From Amazon’s perspective and a capitalist viewpoint they’re doing the most legally required to continue to make profit. They don’t have an incentive to change as people continue to buy their products and the government refuses to step in and help exploited workers, even going to far as to ignore the blatant union busting from Amazon and others when the individuals do try to group together and assert leverage.