I disagree about Mars' importance to some extent because I think it's an arbitrarily chosen destination among thousands of better places we could colonize. Whatever happened to Gerard O'Neil's dream of colonizing the L5 point between the earth and the Moon? What about the asteroids? We know now that there are lots of near-earth asteroids, with plenty of water and carbon.

Focusing on Mars to me reads as overly obvious PR hype. It is very true that we need to set out sights further than near earth orbits, and we do need to establish sustainable off-planet colonies. We should have done so ages ago. Mars could perhaps even be one of those places. But it's not especially good for basing industry, farming, or habitation compared to many other parts of the solar system.

Instead of Mars, imagine how we would develop Mercury. We wouldn't send people, but machines. Maybe some people would settle at the poles (which are cool enough) to help with maintenance or to supervise the machines. Most of the machines would follow pre-programmed instructions with periodic updates to their software from earth. They would collect solar energy and convert it into additional machines and solar collectors.

These swarms of robotics could remain on the surface for some time (covering the whole surface after a few dozen rounds of exponential growth), but at some point would need to move mostly to space to maximize solar power collection. The materials would be shot to space with mass drivers, or high energy lasers from a distance might be used to produce something similar to artificial volcanic activity, slowly shredding the planet Alderaan-style.

Within 75 doublings, a square meter sized initial robotic device would form a Dyson Swarm collecting energy from the entire 0.3 AU radius of the sun.

Autonomous robots can do this in perhaps 75 years, but human colonists won't do it for thousands of years at least (and would need robots anyway). So focusing on "colonization" in the sense of adventurous humans adapting planets to their own comfort is probably misguided. We should think instead along the line of "seed robots" efficiently preparing the way for not only human settlement, but enormous, highly powerful megastructures and coordinated machinery.