This is an interesting question. The moon is only about 240,000 miles away from Earth, while Mars is (on average) 84 million miles from Earth. That is, Mars is 350 times further! So, if it took 3 days to go to the moon, will it take 350 x 3 days (about 2.9 years) to get to Mars? No, it won’t, and here’s why. The moon is traveling with the Earth around the sun, so to go from the Earth to the moon you don’t have to go very fast. Also, you don’t want to go too fast because the moon does not have any atmosphere to speak of and very little gravity. That means when you get there, you have to use a lot of fuel to slow the spacecraft down, to fall into the lunar orbit. Otherwise, you’ll shoot right on by, or worse, crash right into it.
But, going to Mars is different. Starting out at Earth, which is traveling around the sun at 33 kilometers per second, if you increase your speed by just 6 kilometers per second, you will be traveling 39 kilometers per second, which happens to be Mars’ orbital velocity around the sun. So, if you leave at the right time, that speed will send you on a curving arc around the sun to catch up to Mars’ orbit in just 6 months, instead of almost 3 years. And when you get to Mars, the atmosphere can be used to help slow you down, so you don’t have to use a lot of fuel there either. The less fuel you need, the smaller the rocket needs to be to get you there.
So, for a given spacecraft and payload, we can get to Mars using less fuel than it would take to get that same spacecraft and payload to the moon. The politicians who thought we should build a way-station on the moon as a way of getting to Mars weren’t thinking too clearly about that.