The majority of the population on Earth doesn't need to want to go to Mars, only a small minority does. That small minority has to overlap with those who can actually fund it.
Much of the small minority would change their mind when faced with the reality of it. Assuming you actually make it there alive, it will be physically and mentally grueling to continue to exist there. Colonization is a significantly different scenario than manned mission to plant a flag in the ground.
If you asked the early Europeans coming over from Europe to North America if they regretted leaving I'm sure many would say that they did, and in fact many did return. That doesn't change the fact that a substantial number of those early arrivers did stay for the long run.
There may even be failed attempts where everyone dies in an accident as there were failed colonies.
So imagine you're a European in the new world... but also you can't breathe the air, go outside your tiny room, and are constantly being bombarded with radiation.
