Why? Many successful companies are fully unionised. How many people creating content at Disney do you think are card carrying members of a union (the answer: nearly all of them).
That must be why Disney needs to buy Star Wars and Marvel, because they're so great at innovating their own content
Less profits would go to shareholders, which could lower its stock price, but that doesn't mean the company would produce less. More share of profits going to employees could increase productivity and social good to the world. I'm not calling that result inevitable, but possible and up to the company leadership.