Traffic & posts go up and down. Holidays are probably part of it. (I was gone for 10 days!)
The contest might have had an effect, but it's hard to say how much. Believe it or not, the daily hits on the site have been busier in the last 2 weeks (after the end of the contest) than they were in the 2 weeks leading up to the draw date. Hits don't = posts though.