See this here says he organized it. But maybe it had already started and he helped push it.
http://abcnews.go.com/blogs/politics/2012/07/mike-huckabee-calls-for-chick-fil-a-day/
You misunderstand - this issue was much bigger than he was/is - and he simply got in front of the wave. Did he first say”Aug 1?” Maybe, but it was the issue, not Huck’s “immense popularity and clout” that drove it.