If you do some research on the Tylenol tampering it boiled down to a wife poisoned her husband and after it made the news there were a bunch of copycatsObviously, you don't remember the Tylenol poisoning cases, and the subsequent focus on tampering.
What's the point of a secret evil plot, when it's detected immediately?
Always better to do your secret evil plots in a novel manner. Gotsta have style!