That's the point people don't seem to be getting about anonymous reviews- if the review is more costly than the value it provides the seller, they won't do it, and it's fairly easy to make that the case. A separate enthusiast forum where the reviews are from people with a long history of high effort engagement is a good example of that. That's basically the idea behind crypto as well- making false transactions is more expensive than the value it could return.
The law is murky and seems to hinge on the court's opinion on whether the person who committed the crime would have had they not been influenced by an officer. The police being the ones to start the conversation doesn't rise to the level of entrapment. The police deceiving you into wanting to commit a crime may rise to the level of entrapment if the courts find you wouldn't have done it otherwise (the example I found that illustrated this best was "Hey there's a warehouse full of valuables let's go rob it" isn't entrapment but "Hey this guy said he's gonna kill your kid you need to kill him first" probably does absent any reason to believe you would have killed him without being deceived first). My guess would be that the grey area, plus the relative ease with which they were able to secure a life sentence for the other charges, is why the murder-for-hire charges never went to trial.
It made the situation...messy, to say the least.