We know from Trump advisor Rudy Giuliani that some of those leaks were to him.
4) the NY-ADIC
First, Andrew McCabe informed Comey that the NYC office had up to 650,000 Clinton emails on Anthony Weiner's seized PC. And second...
In other words, AG Lynch "ripping" pro-Trump leakers at the FBI may well have been *the* turning point in the 2016 election.
And Giuliani now knew he couldn't get real emails leaked to him, so Team Trump began peddling fake emails.