I didn’t say it was a crime I said it creates liability, this is a civil case about civil liability after all.
For example there are tons of civil cases against businesses that sell ammunition, there are endless such cases against Walmart alone, where the ammunition ends up being used in the commission of a crime.
More often than not Walmart prevails in the ammo cases because there is usually no evidence showing Walmart knew or should have known the buyers intent to use the bullets in a crime (it’s probably true that many times the buyers had not such intent when the bought the ammo). Still there are cases where plaintiffs can prove the seller did in fact know, should have known or even could have predicted the intent of the buyer to use the ammo in a crime.
All that said it’s also true, though far less likely the liability could raise to a criminal level.