Here's my short-ish answer:
Inter spent a lot of money and had no silverware for years to show for it. In Italian conspiracy theory style, they blamed a Juventus conspiracy for their ills -- since they were the reigning most successful team at the time.
Inter, among other conspiracy theorists, turned to the courtrooms to overcome failures on the pitch. After a successive number of years of failure at that too, in 2006 a frustrated guy with some transcripts found by questionable means (wiretaps enabled by Inter board members, today deemed illegal by the Italian government) slaps it in the media through some backdoor attempt at justice.
It got a lot of press, a lot of debate, and raised a lot of cries. Because the game did have shady dealings -- Italian influence style. And the game needed some tighter lines and rules to prevent abuses. Because without them, some teams, Juve's board included, thought the best defense from abuses was a good offense to prevent them. And that became ground zero for referee biases and influence.
Inter got their wishes, as matters were settled behind closed doors within the Italian sporting league and yet Inter was somehow considered of pure and clean hands throughout. But oddly, nothing about the game was changed. No oversight board. No improved rules for eliminating conflicts of interest. The Prime Minister of Italy still owns a club and much of the media that funnels money into the league. So the perception of any clean-up was really just a one-time make-good action, then back to business as usual. Meanwhile, as for Serie A, Inter also poisoned the well in the process.