No, that's not why you alone believe. It's why everyone does. It's the same reason you won't go into a restaurant if there isn't anyone inside, it seems suspicious. But something that is popular seems well tested enough purely because a lot of other people have been convinced. This is how religion works, you don't have to convince every person fully, it's the fact that there is a group of believers that functions as a stamp of approval to new arrivals.
And it's not about being stupid, it's crowd psychology. People affect each other, more than they realize. And it's common knowledge. It's way harder to convince people of something if you can't point at a bunch of other people who have already been convinced.
It's like waiting for the bus. If there are people at the bus stop, that gives you reason to think they know something, they know there is a bus coming. If there was noone at the bus stop, you might think maybe there is no bus, maybe the bus route changed, maybe the bus drivers are on strike etc. You would be a lot more reluctant to draw the same conclusion: that a bus is coming.