Like a car in reverse or a forklift. What makes it feel so unstable?
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Grab a pencil by the tip and let it hang under your fingers. This is a *stable equilibrium*. If the pencil starts wobbling to the left, your fingers pull it back towards the centre with no extra effort from you. This is analogous to steering from the front.
Grab a pencil by the tip and flip it so that you’re balancing it above your hand. It’s harder. This is an *unstable equilibrium* because any change to the left or right will try to pull the pencil *more* to the left or right, and it takes active adjustments from you to keep it balanced like that. This is analogous to having steering at the back.
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Just like how you can *learn* to balance the pencil upwards, people can *learn* to keep cars aligned with steering at the back. Some people who are really used to it might even claim that balance the pencil upright is as easy as dangling it, like with cars. It’s fundamentally not true though.
This is also why it gets exponentially harder to drive backwards with trailers added to the back of your car, but it’s still fine to drive forwards.
It’s essentially like replacing that pencil with a chain, and trying to keep the chain straight. Dangling down, it’s pretty easy (because it’s a stable equilibrium), but it’s nearly impossible to keep a chain stacked straight upwards.
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