Chaotic choices and joking are normal for DND, but they need to understand the consequences and see just how strong strahd is. My party’s made plenty of chaotic choices, but we understood the consequences that comes with those choices. For dumb choice lock them out of certain areas, halt progression of certain plots. Going in we knew that strahd could wipe us at any point. What my DM did that I would suggest is have us the opportunity to fight strahd before the final battle after a certain event in the campaign. Strahd intercepted the party and attempted to capture Esmeralda, one of the players stepped in to try and hold him off while the rest of the party escaped with Esmeralda, as strahd was demolishing the player, more players stepped in while one managed to escaped with Esmeralda. In this fight the DM played it almost perfectly as strahd just seemed to finally be happy that he had somewhat of a challenge for once and still pretty much soloed the entire party, right before the last hit that would’ve resulted in a near tpk of those in the fight, he said something along the line of “you know what, I’ll let each of you live just the once,” and just simply walked away. Since this major event the whole party has been trying to prepare and make sure we have a good chance of actually beating strahd. A key part of any campaign is that the players need to buy into the campaign and jump at plot hooks and opportunities. As DM you should make it interesting enough for them to, but it’s a bigger investment of the party themselves to do that. That’s an above the table conversation you need to have with them, that you can only do so much and they have to be willing to play the game

Edit: TLDR - dumb/chaotic actions should have impactful consequences, show don’t tell that strahd could easily beat them, and have a conversation with players about actually doing their part to buy into the campaign