Dont confuse transmitter power with ERP (effective radiated power). Most mainline TV transmitters are in the order of 10KW, ERP can be 120KW. Satellite transmitters are in the microwave band with very high gain dish aerials, so the power is relatively small. They have to be efficient because they only run on solar panels, hence low output.
Most Satellite transmit on a very narrow beam compared to Terrestrial transmitters. And of course at the receiving end you have a very high gain satellite dish with an active LNB to boost the signal even more. By comparison Terrestrial antenna are very inefficient.