Boxing is basically dead, at least heavyweight boxing is, which drives the sport. I don't believe pay per view hurt boxing though. In fact, if it ever makes a comeback, pay per view revenue getting the boxers big purses is probably its best chance.
IMO boxing has several problems:
1. Its too dangerous. There is only one sure fire way to win a fight, that is to knock another fighter unconscious. With brain injuries coming to light as they are, how much money would it take a person to risk the health of their brain for the long term? Prospects are going elsewhere.
2. Boxers are basically independent contractors, some sell their services to organizations, some to promoters, some to cable providers. There is no uniformity. You have to get 2 guys and their camps to agree on venue, purse, date, etc and thats not easy. They know they are going to get a pay day somewhere so they can wait to do it on their own terms which often don't line up with quality opponents that fans will pay to see.
3. While the fighters are independent contractors and can make millions, they want medical paid for by the promoters and/or boxing organizations. That's probably never going to happen. Many boxers can't get medical insurance. Its not a wise investment for insurance companies. Millions goes fast when your in the hospital with head trauma and no insurance. For an up and coming boxer not making big money, this has to be hell on Earth.
The UFC has several advantages IMO:
1. While the UFC is a brutal sport, is not near as dangerous as boxing. Fights are much shorter and there are many ways to win fights that don't involve rendering your opponent unconscious. Its easier to live life after fighting with creaky knees and ankles or bum shoulders than it is with brain damage.
2. There is one company with their fighters under contract and there are very few decision-makers. If White says you're going to fight so and so, its going to happen or that guy is probably going to lose his contract.
3. Dana White. I believe White has studied boxings mistakes and has learned from them. He promotes his fights well, has a network contract which brings his sport to the masses for free, and makes fights fans want to see. He also is using the small regional promotions as his minor leagues to develop fighters.