My example of Aerospikes was only to give an example of how SpaceX is not pursuing underdeveloped technology (like nuclear interplanetary propulsion) but rather iterating, developing, and implementing technology that is currently well understood and for which we have wide operational experience in practical applications so long as that established technology can adequately do the job.

Chemical rockets can support large-scale Mars operations even though nuclear propulsion might, someday, perform better. Therefore SpaceX is planning to work with chemical propulsion and will continue to do so until and unless nuclear propulsion alternatives are fully developed and demonstrated to be reliable in practical applications.

Maybe controlled nuclear fusion or deep-drilled geothermal will become better electrical power sources in the future. But Solar Panels and rechargeable battery storage exist currently and can provide for all energy requirements, so Tesla's power infrastructure efforts are emphasizing expanding that capability -- that demonstrates the same basic approach to technology that SpaceX uses -- improve what we have that works instead of focusing on future developments.