What is in place to stop systematic fraud from occurring that would also allow three old geezers in the Villages to pull it off? Somehow, they were able to commit the fraud in the first place which is what I find disturbing. It tells me that if they could do it, a systematic effort might also succeed. It might even be more likely to be successful and less likely to be discovered if those attempting the fraud were better equipped to cover it up, less likely to be discovered.
I don't consider that punishing fraud after it has occurred, and the fraud has accomplished its intended effect, deals with the issue. Being caught after the election results are finalized would mean that the effort succeeed in its goal. Suppose at some future time, seeing that the three old geezers were able to successfully cast fraudulent votes, that a more organized entity decided it would be worth their time and effort to use similar tactics? Even if detected months later the results would still be the same and if the more organized entity were a bit more facile at a cover up than the three geezers it might not ever be detected.