a car can still balance if you rip one of the wheels off
do the math
It may slightly tilt, but remove the other front wheel and what happens? It falls on it's front end
When Rainbow Dash lifts her front left hoof to step forward, both her front hooves are in mid air-- oh wait, looking back at the gif, Rainbow Dash DOES go forward a bit like she's gonna fall over, but she moves her hoof fast enough that she can stop herself
SO MUCH DETAIL