Did you notice who was sitting right beside Rep. Stefanik when she ambushed Comey? I’ll betcha a dollar to a donut that Gowdy coached her along. They threw Comey a question he didn’t anticipate, choked and threw Priestap under the bus. If he hadn’t cooperated before Priestap probably speed dialed his lawyer to work out a deal before he got grilled under oath from Republicans smelling blood in the water.
That's my take.
Thank you, Comey.
p.s. Why Comey thought it would work is a puzzlement to me. Since when does the boss take orders from a subordinate. Comey is toast either way.