Ok, so, there you’re right to some extent. Certainly the article does attribute the decline to the mosque controversy.
I didn’t look close and see where he was before he was at 41%
41% does seem low for a Gallup. Certainly, being in favor of a mosque at or near ground zero is not going to get votes. I’m not sure that being against it is going to get votes either, but if you had to choose one, being against is better.