So many reasons:
Hillary had no part in the production or publication of the Steele Dossier. It was a"Third Party arm's length transaction". Trump met with Pecker, and directed the "catch and kill" scheme, and provided dirt and rumours on the opposition, all of which were published by the National Enquirer.
The Democratic Party took one look at the Steele Report and they gave it to the Republican Party, who gave it to the FBI. The Clinton Campaign made no attempt to use the material in the Steele Dossier against Trump, nor did they publish the report.
Nobody was doing anyone any "favours" in the production of the Steele Dossier. Steele was paid for his work, as was Fusion GPF, and the Democrats lawyers. Pecker's purchase of Karen McDougall's story, and that of the doorman, from his company's resources can be considered an illegal campaign contribution.
Hillary isn't on trial because she did nothing illegal. Trump deliberate set out to deceive the American people, using the Enquirer, lying about his opponents - on purpose, accepting the campaign gifts of the catch and kill payments, and then trying to claim the payments as a business expense.
And as always, it's that attempt to claim the payments as a "business expense", that got him arrested.
