Twitter is displaying more tweets from profiles that users do not follow.

There is plenty of opportunity for increased exposure here, and Twitter wants to keep users in the app for as long as possible to boost interaction, which these suggestions should theoretically enable.
It’s similar to how Instagram and Facebook are now displaying more AI-based content suggestions, which originates from TikTok’s focus on emphasizing the most relevant material to each user, which isn’t directly related to your social graph.

There was a period when your social graph was the defining element, giving Facebook a major edge, but now there’s a larger trend toward entertainment over social engagement, which extends the possibility to display each user more fascinating stuff from a far broader range of sources.
It makes sense logically, but it is heavily dependent on the platform algorithms being effective at delivering you the greatest material based on your preferences. TikTok excels at this, capitalizing on your declared likes and dislikes based on your viewing history.