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