My quiet introverted friend became very talkative

I have a close friend that i've known for more than 10 years, he was usually quiet and doesnt engage a lot in conversations with strangers, he's fun to be around and he listens more than he talks. When i went abroad to study, i came back after one year, and noticed he became very very talkative, talking about all sorts of things, laughing and complaning about a lot of things with no filter. I've been thinking about what made him change. I even told him that he became more talkative, he responded that its okay and that we need to express ourselves more.

It still bothers me how he changed this much, and wondering how?

NB: he's 25, lives with his parents and works as an engineer.