What originally attracted people to platforms like YouTube and Twitter?

They've changed since they originated, and we need to distinguish between what these platforms are offering today and what they offered in the past. The fact that Twitter now allows people to post larger amounts of material doesn't change the fact that you could only post smaller amounts when the platform originated. And now that people can post more, how many users make use of that feature? The large majority of users don't post anything. And among those who do post, probably the large majority of those individuals still just post brief comments, often one sentence or a fragment of a sentence, typically without any supporting arguments, documentation, etc. And when a user posts something lengthier, there will often be complaints that it's too long, even if it's only a few sentences or some other small amount. Similarly, the fact that you can get somewhat good transcripts of YouTube videos today doesn't mean that you could do so when YouTube originated or that more than a small percentage of users access that feature now that it's available.