I don’t think they could actually stop such a technology from being deployed on earth in such a scenario. Nor do I think they would really object, it seems doubtful to me that they would all want to go to mars, and for those that don’t, trying to prevent it’s use is counter to their interests.
The technology to allow them to live the kind of life they would want on Mars would also greatly decrease the human impact of the climate crisis applied to earth. A mars colony fundamentally requires the ability to insulate an entire city, to ultimately civilization, from a climate more inhospitable than we could render earth even if we burned every scrap of coal and oil in the ground, and a billionaire would probably want more than just that bare minimum functional civilization to live someplace.
I’m not sure malls really are a “pillar of capitalism”, something akin to stores will exist in virtually any economic system, because ultimately their function in the economy is to distribute the results of production to individuals that need it, regardless of who exactly owns or profits off them, and the need for a function like that is virtually universal.
What malls are really is an attempt to recreate the experience of a busy pedestrian street, for a place that is heavy on car use and so doesn’t have many of those spaces. Hence you get a bunch of shops together in a space that lets one conveniently walk between them.