I doubt they're creationists because not too many educated people of any stripe are creationists, but I'm really failing to see your point.
Suppose the NASA program managers are actually all creationists; they'd STILL be looking for life on Mars, because if God were going around the universe creating life, He would probably do so in habitable places. Mars is the closest place to us that could conceivably have been habitable to life at some point in the not-too-distant past.
God did indeed create life in a habitable place, the earth.
But on other planets? No reason from the Scriptures to think so, so whether creationists would spend billions of dollars hunting for life on a planet that has given no evidence for life in its past, distant or otherwise, is questionable, to say the least. I won’t speak all creationists.
As to motives and beliefs driving the present search for ET life, it’s been made abundantly clear that it is the desire of Darwinists to demonstrate that life could and did arise sans God on earth.