I was wondering if someone could share games that started in a game jam then went viral and preferably fully released.

You can see them here https://itch.io/jams/past.

Baba is You was made for for the Nordic game jam. That's the only one I can think of off the top of my head.

While not fully released, Baldis basics started as a jam game, and so didn't Friday night Funkn'.

https://vlambeer.itch.io/nuclear-throne started out as a game jam game: https://vlambeer.itch.io/wasteland-kings

Hollow Knight, although not too much connection.

Team Cherry made "Hungry Knight" in a Jam and decided to take the character and some of the art direction from it forward into its own game