Meta's mission is to build the future of human connection -- this totally makes sense if you assume they believe that the future of human connection is with an AI friend.

That https://character.ai is so enormously popular with people who are under the age of 25 suggests that this is the future. And Meta is certainly looking at https://character.ai with great interest, but also with concern. https://character.ai represents a threat to Meta.

Years ago, when Meta felt that Instagram was a threat, they bought Instagram.

If they don't think they can buy https://character.ai then they need to develop their own version of it.