By Tobias Carroll Last year, news broke about a high-profile Ponzi scheme targeting independent film investors. The guy behind this was named Zach Horwitz, an actor who worked under the name Zach Avery; all told, he’d brought in $690 million for a host of distribution deals that promised absurdly good returns but turned out to, you know, not actually exist. Later in the year, Horwitz agreed to plead guilty. All of which begs the question: just how did he get so many people on board with this plan? A new article by William D. Cohan in Air Mail offers some answers — and, as it turns out, it invo…