> Agreed, but enabling folks to get there makes it possible.
It doesn't. Getting a few people to Mars alive does not a colony make. And even that sentence is misleading because while getting to Mars orbit is certainly challenging but that's something I can see humanity capable of overcoming with current technology. Although we never kept humans in space for 2-3 years before which is just the travel there so we don't really have any idea what will happen to them but let's pretend.
Landing very fragile humans on Mars, however, is a much, much formidable challenge. The heaviest object we have managed to soft land on Mars, so far, is the 1025kg Perseverance rover. The Apollo Lunar Module carried two people and was 4280kg dry weight. Of course, you don't need to ascend -- getting those people back to Earth is not even considered by anyone sane -- but still, it shows there's a problem here. And that was two people. And you need everything for them to live on the surface, including air and water and that's even more weight that you can't just slam those into surface at the ~20 000 km/h the spacecraft will approach either.
It would be just about infinitely better if he tried to show off with climate change combat projects. If you want to show off, a vast forest would be much better, much easier to achieve and so much cheaper. He could build storage for renewable energy, these are also sufficiently massive to be good for showing off. And so forth. There are easy but significant things one such as him could do. For a more formidable challenge, elevate the Brazilian people so they don't need to burn the Amazon.
We already have a terraformed planet but the climate is changing in a way which is incompatible with the way humanity currently exists. It would be prudent to change both -- while the change is inevitable it could be slowed and humanity could change too. Once we bought time, we can wait until material and other sciences make space elevators possible and then we can send robots to Mars to build a space elevator too and then we can begin to think about colonizing Mars.