Another possibility is that TikTok's short-form content feed allows for a greater volume of feed to fit into the same timeframe. Twitter was popular because it condensed blogging into microblogging; TikTok's success is pretty easy to delineate from that logic. Even if you don't have an algorithm promoting enjoyable/affirming content, you're just more likely to encounter that content when you watch more videos.

Whether that behavior is healthy or not... I'll leave that up to people more educated than I. My guess is that trading the user's attention span for short-term engagement isn't worth it, though.