The Hush of Expansion
The largest surprise encountered by those intrepid explorers was that so far the galaxy has turned out to be entirely sterile. No signs of any previous life have ever been discovered: no first contact; no signs of intelligence or evidence of civilisations; not even a single bacteria on a distant moon.
The knowledge that we are almost certainly alone in the universe has not always produced good outcomes in the human psyche. There are those who took this as the final proof that the universe was created for solely for us by this or that divinity. On the other hand, there are those who take offence at the unrivalled expanse of emptiness, and have simply gone mad rather than cope with the concept of infinity.