Let me throw a little bit of perspective for ya here though. Let's say one of our videos goes viral, and becomes an overnight success, 2 million views over night. If you and I weren't vloggers, and it was that video of our cat doing something adorably cute, you would be totally right. But the thing is, if people like one of my videos, they're gonna like more of my videos, and if 2 million people see me overnight, alot of those people will sub to me, which means they will keep liking what I'm putting out, which means as long as I stay consistent and keep doing what I'm doing to the level I'm doing it, my videos will keep being seen by tons of people, and making me money.
If you were a one trick pony, I'd say it was a huge gamble, but when you're multitalented and able to keep delivering, it's really not.