It's about our attitudes towards time, and the stories we tell about our relationship to it. For example, authoritarian regimes tend to eliminate the future from discourse - the future is not possible because we are beset by enemies and danger surrounds us. All we can do is aspire to restore some mythical past. By contrast, the one idea that ties together disparate definitions of Progressivism across history is the belief that a better future is possible.
Snyder has a framework for discussing how ideologies relate to time in these sorts of ways.
Well yes, kind of, and in conclusion no. Certainly the mythical golden past is a component of populism, and can be seen in Mussolini wanting continuity with Romans, and Putin weaving his own myths about Russian history - I forget the details, but it entails more territory for Russia because historicist destiny - and "Little Englanders" (the look-backward, xenophobic kind, not the original ones who were just isolationists).
On the other hand, Musk kind of likes looking toward the future. So this thing about a mythologized past is at most a tendancy, and a way of stirring up a sense of injustice, while your non-authoritarians don't have the monopoly on looking to the future. In fact I don't see that these are even polar opposites, I think authoritarian progressives would make sense as a concept, and we may be seeing a bunch of them rise to power.
Snyder has a framework for discussing how ideologies relate to time in these sorts of ways.