Both knives designed for stabbing people and guns and bullets designed for shooting people exist and are sold in the US and I'm not aware of their manufacturers

Both knives designed for stabbing people and guns and bullets designed for shooting people exist and are sold in the US and I'm not aware of their manufacturers or retailers generally being held liable when they are used to commit crimes. I don't think your analogy holds. Selling drugs is victimless in the sense that there is no legal ''victim" bringing a complaint - both the seller and the buyer are generally willing participants in the transaction. This is why so many drug prosecutions must rely on stings, undercover cops, informants, surveillance, etc. This is not to say that nobody suffers any harm as a result of the drug trade. In this particular complaint there is no victim and all the evidence comes from undercover cops and informants.