It’s Obama. He went stark raving mad with hatred for Donald Trump. Obama intended to destroy Trump before leaving office and when, shockingly, Trump won the election, Obama was desperate to get something on Trump before it was too late. But, Trump was clean.
As POTUS, he was drawing a salary, during the Trump campaign.
I’m assuming it was someone volunteering for the Trump campaign and was appearing to be Trump friendly. They’d have to be in order to have any access to meetings, etc. So they volunteered then, but are on the payroll now.
Kushner comes to mind, but I certainly can’t see him working against his FIL for the FBI. Steven Miller? Nah. I don’t know enough about his volunteers.