Dogs are social animals, and they expect to fit within a social hierarchy.
They will push to establish their position in the heirarchy.
I have seen chihuahuas establish dominance over much larger dogs.
Occasionally the pit bull next door (nice dog) gets loose and runs over to our house because Mr. GG2 always gives her dog biscuits. One night our Chihuahua was out on the deck and the Pit came running up to our gate. Our dog charged off the deck and ran up to the gate and the Pit dropped, rolled over and put all 4 feet up in the air. She never moved til finally our Chihuahua “released” her by turning away. It was hysterical.