Except there has not been one example in ALL of recorded history, from ALL regions in the world, of one "ruling class" or "elite" or "ruling family" or "oligarchy" of staying in power beyond say ~500 years at the most extreme (let's put aside San Marino and Monaco). I find this theory not plausible.
You couldn't be more wrong. Just look at the French royal family. It's was always the same family (and the same Y-DNA lineage) from Hugues Capet until Louis XVIII, nearly 1000 years later. The family was divided in various branches over time (Valois, Valois-Orléans, Orléans-Angoulême, Bourbon), but they all descended from the same patrilineal ancestor.
It is almost impossible to go back more than 1000 years using a paper trail as there are few written sources left from the Dark Ages, and also because Germanic people overthrew the Roman Empire.
But genetic genealogy is a powerful enough tool to tell us that all these R1b-L11 derived lineages in European royal families descend from a common ancestor who lived about 5000 years ago. So it doesn't matter if we can't connect them through a paper family tree, DNA doesn't lie (and for that matter a paper trail can lie or be mistaken or suffer from non-paternity events).