An important piece of the puzzle.
No puzzle at all. Every Senator up there who was trying to turn Sessions (and last week, Coats and Rogers) responses into "stonewalling," was gaslighting. The principle that Sessions was relying on is well known, established, and if not for assholery, not contentious.
Juvenile showboating. It's a shame that the public tolerates this sort of low-life rhetoric from powerful legislators.