He's just incredibly chilled and entertaining. He never takes it badly when people make fun of him and constantly laughs about himself too.
He also takes the time to read live in the stream every single donation and welcomes live every new subscriber. He's also married and his wife plays CS with him many times, which also generates a lot of funny situations and dirty comments on the chat. Which, once again, he never takes badly.
It's just a lot of small things that he does right, but the main reason is because he is just a really likeable guy I think.
He says it all the time he has no clue how his channel got so popular. People ask him all the time how did he manage to get so big and always answers "To be honest, I don't know...". And I believe him lol.
He doesn't only play CS, from time to time he will try the newest games out there too.
At the moment, apart from CS he also plays H1Z1 and DayZ.
Fanboy.