official mail

I had to send an email to 10+ folks at office and gather their response. I sent one email addressing them in general and cc-ing bunch of managers. I didnt get any response.

Then I sent 10+ emails. Directly addressing them, placing their name in the subject and cc-ing none. An email was sent to one member only. I got response from all.

Just wondering what is the key behind this situation. Did they respond because they are directly responsible and hold accountable? But managers were not informed, so they could have deferred.

Anyway I got what I wanted and a new technique to apply at such scenario.