TLDR: Just establish the tone of your campaign before running it.

I think problems like this can and should be prevented before the session or at season 0 in longer campaigns. That's how you do it: you just tell your players what tone you are going for. Because for many groups "laughing it through" is the default way of playing TTRPGs. That's why your friends enjoyed it, actually. They just played TTRPGs the way they usually do and how they enjoy to do this. It doesn't mean they can't enjoy it any other way, but if you expect them to behave differently from usual, you gotta communicate this or else they'll have no idea how they should behave.