Musk has never, no matter what he claims, ever a progressive democrat. He would be at best, someone who believed in the liberalization of certain drug policies. His economic beliefs have always been max pro business (aka, hands off, anti labor). He solidly fits under libertarian like the rest of the tech billionaires. Republicans, if it weren't partly driven by Christian fundamentalists, would be libertarian. The conservative GOP party of the 70's hasn't existed in decades.