When the government investigates an individual or organization that has long been known to be corrupt, I always think 'why them and why now?' For example, recently they took down a local politician known for corruption for decades; why now? There are other similarly corrupt local politicians; why not them?
Why is the FBI taking down FIFA and not the Catholic Church, which operated a global child rapist protection racket, or Wall Street firms, whose financial fraud harmed billions of people and nearly took down the world economy? FIFA's crimes seem to have relatively minor consequences.
My working hypothesis is that the corrupt lose key political protection and then their enemies pounce. But I don't really know.