losses are proportional to current squared and to resistance.
More specifically, P = I²R
So you can reduce the resistance, but that you can take only so far as the wire gets thicker and thicker and heavier and more expensive.
Or you can reduce the current. You can take advantage of a property of transformers, that they can increase voltage while decreasing current, keeping power (product of voltage and current) constant.
If you step up the voltage by 10 times, you reduce the current by 10 times, and this reduces the power loss by 10² or 100.
If you step up the voltage by 100 times, you reduce the current by 100 times, and this reduces the power loss by 100² or 10000.