Didn't follow the news at all for some weeks now, but when I told you weeks ago he will probably sign here, I wasn't making things up.
Everything was almost done, and both PSG and Juve just waited for Matuidi's decision. His family loves Paris, and wanted to stay there, but he still didn't accept the fact that PSG didn't want to keep him at all cost (they offered him a contract extension, but also said he's free to leave, which hurt him a lot).