It was a procedural vote. There’s a Senate rule that says a bill cannot be resubmitted for a vote for a certain period of time after it has been rejected — unless the Senator who sponsored it votes against it. McConnell sponsored the bill, so when it was clear that it couldn’t meet the 60-vote cloture threshold he voted against it just so he could bring it up for another vote at any time.
Thank you for clearing the fog with that description. I knew it was something along those lines, but since parliamentary procedure is exceedingly arcane, many incorrect motives tend to be inferred.