Because he only doesn't get confirmed if he says something inflammatory. Say nothing at all and it's a "Team Red vs Team Blue" vote and he has the numbers. Gorsuch was the same way and all future hearings will be carried out in this manner because it will always be party line votes.
McConnell started blocking all Obama nominees, so Reid nukes the filibuster on those so it only needed 50+VP, which got the nominations confirmed, but removed any ownership in the process from the opposition party. Pompeo doesn't need any Dem Votes do doesn't have to say anything or answer any of their questions legitimately because he doesn't need them. He needs to keep 50 Republicans happy, and they default to support him unless he says something that blows up in the MSM. Say nothing and he's confirmed.