What reason does Langdon figure out that caused Fache to frame Langdon for murder?

Langdon, trying to figure out why he is being framed for murder, finally figures out how Fache chose him to frame. He discovers that his editor had sent an advanced copy of his controversial manuscript about goddess worship to Fache, which also revealed that Langdon would be in Paris. So, Fache, the Teacher, was able to master plan Sauniere's murder, and even had someone to frame for the murder--Robert Langdon.