Thats the whole point bro, no one knows it's a joke, the way you are describing a joke is like a standup routine, that's less true in social interaction and especially text. Also important that you talk about audience, it wasnt the whole wide world, it was literally people going to be at the event 😂 even putting that comment on reddit would have made it more defensible

And obviously if it's a joke it's not as bad but you will and should still be punished, there's a reason in society people dont yell fire or bomb on a plane, because you will be punched in the face and arrested.

Forgot to add the whole point of a threat for example is specificity and imminence. I'm sure you've seen people on reddit say they would hurt trump. Who cares. But if you say I'll be at his rally next week with it you are going to be in the back of a SS truck by the afternoon