Any good sports executive knows you need to be open to any and all scenarios when presented with them. In each sport, there are very few players who are truly untouchable. Otherwise, almost all players will be listened on in trade discussions, no matter how unlikely a potential deal is.
When Jorge Castillo of the LA Times initially reported the Cardinals and Dodgers were talking about a Nolan Arenado trade, it seemed like something out of left field. Sure, random national writers had been suggesting the Cardinals should blow it up, but it was all speculation and unfounded at the time. Now there seemed to be real smoke to the rumors.
It was later confirmed by others, including Cardinals' beat writer for The Athletic, Katie Woo, that talks did take place between the two clubs. So how on earth did that even happen? Why would the Cardinals even let a conversation happen if they were not intent on trading Arenado?
As Woo and many others have indicated, it's exactly what I started this story by saying. Every good front office executive does their due diligence, especially when a club has disappointed as much as the Cardinals. Sure, they had zero intention of trading Arenado. But what if the Dodgers were going to absolutely blow the Cardinals' socks off? What if Los Angeles said, "You can have 3-4 of our pitching prospects, just tell us which ones you want."?
It doesn't mean St. Louis would do it, but listening doesn't mean anything more than that. It's just listening. You can come talk my ear off about any subject and try to convince me of it, and it does not mean it will change my mind. But on the off chance it does, why not be open to it? In all honestly, the Cardinals likely wanted to see if they could acquire some great pitching prospects for a combination of their free agents to be, and the Dodgers rightfully wanted to see if Arenado was available. If the Dodgers were sellers right now, I'd hope the Cardinals would turn their conversations from impending free agents to guys like Mookie Betts too.
John Mozeliak finally came out and shut down the trade rumors. and although I too wish he did that sooner, I think some fans have taken that as evidence that discussions never happened. Per reporting, discussions did take place, but as Mozeliak has said, they have no intention of trading Arenado, and if there was a 0.01% chance when the Dodgers were asking, now the chances are 0%.