The NASA administrator is a political appointee, so they will be as religious as the president wants (or allows) them to be. Positions like these are sometimes given as reward for loyal party members who supported the president’s election campaign rather than the most qualified candidate.

However, Bill Nelson is an astronaut so he probably is the most qualified (politician) for the job. I’m sure he works hard to get NASA the funding it needs regardless of his personal beliefs (and it would be illegal to make atheism a job requirement). Aside from awkward speech giving I think most people are optimistic about how he’ll do as administrator.