The evidence comes from what happened to Microsoft when it faced its own antitrust troubles in the late 1990s and early 2000s.
Microsoft ruled computing in the mid 1990s. By 2010, it was an also-ran. All that happened despite the fact that Microsoft escaped being broken up, and also avoided crippling fines.
Google now faces the same potential problems (forced divestiture and huge fines). Some day, when the case has run its course, Google is likely to be fined a relatively small amount, and will have avoided any danger of a forced breakup of the company.
But Google’s momentum will have been halted. And if precedent serves as guide, Google never again will “lead” computing markets.