Or, the less mean dogs were lucky that humans only killed the threatening ones?
Like… wolves?
Most wolves are actually terrified of humans and would probably run away if they see you. You should still be careful in areas with wolves though.
Little dogs are mean because shitty humans think “aw he’s so itsy bitsy I don’t have to train or discipline him at all!” Totally ignoring that (a) a dog needs maintenance discipline to be emotionally secure, and (b) aggressive little dogs are unhappy little dogs.
Luck’s got little to do with it. Dogs were selectively bred for those traits.
My mom and sister have chihuahuas and my grandfather has a shih tzu, they are all super sweet dogs who have ever been aggressive towards anyone. Meanwhile, a family that lives down the street from my grandfather had a golden retriever that had to be put down because it kept attacking kids unprovoked. Sure, some dogs are more predisposed to be aggressive than others but the way they are raised and the environment they live in plays a massive role in how a dog acts.
Are bigger dogs less mean, though?