Smaller dogs are more aggressive because they are fearful of bigger dogs, so it’s not a true aggression, it’s a fear response, mostly.
When I was a little tyke, while the family was camping at Bear Lake, we cowered in our tent and watched outside as a rather large bear dug through a nearby trash can, only to see a tiny dachshund chase the bear away yapping after it as fast as the little noodle could run.
Little men seem to pick more fights too!