Maybe we can practice for Mars by first colonizing Antarctica or the Continental Shelf. Sort out dealing with Martian like temperatures/lack of breathable air first. And work on safe, economical, and relatively clean nuclear energy as an existential priority.
We call it nuclear waste but the stuff has the potential for all kinds of neat inventions using it. Why has that not happened? Because nuclear radiation is very efficient at killing things.
It needs only tiny amounts of energy to kill you and it has enough energy to do that for centuries! So Governments here keep that from happening and I don't blame them from doing so. In space you have a different story .
In space you are surrounded by lethal natural radiation all the time. By necessity you have to monitor it and because space is mostly vacuum you have to live in protected man made enclosures. Creepy people doing creepy things with nuclear waste in space environments is not the same threat it is to us in our protected bubble of life we call Earth.
Musk has devoted his whole life to expanding Civilization into space .Once Civilization is established off planet the people there will invent all kinds of wonderful things using radioactive stuff . Musk is creating the very thing which will eventually solve our energy problems for centuries if not longer.