> Several people on the team confronted the CEO, but he denied that there was an acquisition brewing. If there actually was an acquisition brewing at that time, and it's true that the CEO denied to employees that there was, that's one way to spoil any existing culture of honesty and goodwill.
It's probable that he was legally bound by a confidentiality agreement.
If already under such an agreement, find a way not to lie.
Being proactive can help. The first example that comes to mind was when a highly-placed colleague (who I trusted, and with whom I had a good rapport) asked me directly whether I knew whether of anyone in the department who was job-hunting. I didn't know of any, but I told them I generally couldn't answer that question, as a matter of policy. Because that's the kind of question for which we can anticipate a hard conflict someday, between betraying a trust, and lying to someone else. And that's an easy conflict to avoid.
"If I knew, I probably couldn't tell you." is a useful phrase.