Anyone who answers other than 1 and 2 is on YouTube for the wrong reasons. It's 1 and 2 that make 3 and 4 possible yes, but it is hardly a certainty.
For me it's definitely 1 and 2. I have passion for visual media, and it is an awesome hobby. While I have broken trough 700 subscribers I hardly call myself famous, and $$$? Hahaha! All things considered I am probably negative $1000 dollars with how much I have spent on my hobby.
It's all about having fun!