Keep in mind:
Horowitz worked his way to being FBI IG by being a "Company Man". As such, his main objective was to coverup and whitewash any DOJ or FBI organizational "sins". To make his "investigation" somewhat believable, he threw those already know to be guilty like Strozk and Comey to the wolves, while preserving the "Agency".
He's not likely to show enough provable criminal activity by the clinton crime family to warrant indictment. Hey, he like living as much as the next guy!
The swamp always puts one of their own in as the inspector general for their organization.