You have to set the hook before you reel them in, anon.
It's almost like before you can bust them for stealing an election, you have to let them, ya know, steal an election.
….or let the drug dealers sell you a few kilos of coke, and wait until the product and money has exchanged hands until you spring the trap.
Stupid people should be careful with analogies, they tend to get carried away and use them inaccurately.