[Universal110]

Just to be clear i'm not asking how to dox someone. I'm asking this so I could learn how I could protect myself from doxxing. Just as an example, a popular youtuber named "Dream" got doxxed, he had almost everything leaked from his ssn, number, and address. Even some of his family got doxxed as well. How does someone do this? There was not much public info on him but they somehow managed to get all of this information.
-Thanks