Given post-9/11 history, they could have enticed him into overt preparation for the crime they were tipped off that he might be prone to commit, arrested him for it, and claimed it as a foiled terrorist plot. But regardless of whether it would have actually been a something-like-accurate claim in this case, he wasn't Muslim, so the resulting headline wouldn't fit with the acceptable narrative, so there was no motivation to expend the required resources.