Narcissist ego is a helluva drug. On one hand he is busy manufacturing and erecting the ornaments of a 'great man of history' legacy e.g. renaming concert halls, etc. With the other hand he is accelerating the end of US hegemony by crippling the world economy and showing the world his ass via strategic loss to the plucky Iranians, which will be his actual legacy.
It's notable that none of the superficial ornaments of the Nazi regime persisted and the ideology essentially evaporated like a bad dream after 1945. The legacy of that regime was the popular determination never to repeat it. That would also be appropriate for MAGA.