The broader US market is only about 25% bigger than the S&P500, FWIW. (Or put another way, S&P500 is about 80% of all US equity.) They also trade in almost lockstep:
This is specifically one of those points in stock history where it isn't true; the heavyweights of the S&P 500 are dragging it down while the smaller companies are less affected.
I brought a graph in my earlier comment! Even over the past year, they're highly correlated. (And the S&P500 is ahead over the period -- not the other 25%.)
This is specifically one of those points in stock history where it isn't true; the heavyweights of the S&P 500 are dragging it down while the smaller companies are less affected.