I had the same thing happen, but both they and I were Facebook users, it's just the algorithm decided I don't need to see posts from my friends and it's better that I see adverts (I can live with that, I don't pay to use the platform after all) and hundreds of random pages/groups that I have zero interest in following.
This 2nd "feature" is slowly driving me towards the point where the FOMO of no longer passively interacting with my friends may longer keep me on there.