Most social networks started to do this, or at least marked it as a'feature' due to friend creep.
Users were liking / friending too many things so anyone with over 250 interests that could populate the feed were giving people FOMO stress/anxiety. When it took you 2-3 hours every morning to catch up on last night, you'd slowly stop using Facebook/Twitter/Instagram completely. So the pitch was "We'll show you what you care about most"
It was based on how much time you spent on that page or what kind of posts you engaged with (liked/commented)
so initially, people loved it because they'd see an update from Volkswagen and 2-3 posts from their immediate family before the feed became less relevant to them so hopping into Facebook every hour for 10 minutes was more effective.
...but what really happened is that Facebook used that data to know when to insert ads, what colors to use, size and kind of ad so they know after your mom's post, it goes to your sister's and between those is an ad that looks similar to those 2 family member's post and you do read it instinctively.
Most recent is less profitable for Facebook in many ways.
