Not to minimize what SpaceX has done, but building reusable, reliable, relatively-inexpensive rockets is a far cry from building a sustainable colony on another planet.

Musk may be able to eventually manage the latter, but I don't think success at the former is a reliable indicator of that.

Reliable would be a strong word, but SpaceX has certainly demonstrated its ability to innovate and reduce expenses at the same time, which is a necessary condition to even entertain the idea of interplanetary flights.

They also seem to be fairly concentrated on development of new vehicles and don't distract themselves with anything else.

I also don't expect Musk to be able to build a sustainable colony on another planet, what I do expect is for him to be able to build the transport infrastructure that enables someone else to be able to build it[0].

And even then, most likely with a layer of indirection that puts Starship in the role of space truck which enables the infrastructure be built, but which isn't the main mode of transport itself: To really make a Mars colony viable, I think both Earth and Mars (for different reasons) would probably want a non-rocket launch system such as an orbital ring, which Starship could help build.

[0] assuming the von Neumann replicators don't eat us all first. He is literally building a bunch of general purpose humanoid robots and suggesting they may take on factory roles… and Tesla/Optimus isn't the only such robot under development.