Great post! My thoughts is that BTC dominance is an important short term indicator of the sentiment of investors. Like stocks, when the market is uncertain on the direction, most investors will go to quality names. This will mostly likely be Bitcoin and other bigger names. If sentiment improves then most will go to other altcoins as they believe they have more potential to increase vs BTC. Also, consider that most altcoins do not have fiat options to purchase; most need BTC or ETH to be purchased so when overall market increases, BTC will likely be sold for altcoins.
Thanks for the input. It makes sense to me.