This has always been done, people reuse jokes but in a different context or a different plot twist. One of the best examples being 3 people walk into a bar, puns and wordplay, knock knock, one-liners (I used to think I was indecisive, but now I’m not too sure), etc… I bet you most jokes that have been told have already been told at one point in history, quite hard to make new original ones.
Studying mimicry is literally a whole anthropological field. There are a ton of social signals, types of informations and performances that are shared and played when people engage in the same jokes and trends. Also, I think the term “there is 0 originality” has been said… quite a lot, over many generations. You can find out more if you read the book Algospeak.
Consequence of social media, theft has become easier and more wide spread. But joke we’re still being borrowed from family members and friends and told elsewhere, social media just made it easier for people around the world to access it. People stealing jokes from each other has been a common practice since its conception, it’s just easier now.