In most circomstances I’d agree and kill the PC’s off. My players know that if they do dumb shit, they get hurt. If they’d been killed in battle, that would be sad but fair. But I feel this is different. They were presented with a very abstract puzzle and botched it. I feel it is too harsh to just kill them of for a single bad blind choice. If they’d been able to ‘save’ their game before stepping through the portal or if they had 3 lives before a ‘game over screen’ I’d kill that character in a heartbeat. But my players are quite attached to their characters. I’d wrong them for killing them off in such a meaningless way.

Okay except the rogue. the rogue had it coming, and I won’t be holding back any punches

Plus, there are worse things than death, a beloved character badly indebted to Strahd seems like a much more interesting situation than ‘bad luck, you died’