Earlier quoted context omitted.
Corporate earnings have been flat for over a year, so they don't really explain why the S&P 500 still went up 15% from the 2018 highs. And now expectations are down substantially and even for 2021 are below 2018 levels.
if a $100 billion dollar company generates $10 billion of profit annually, then that is 10% returned to shareholders every year even if there is no earnings growth.
But that doesn't explain why the price you pay for $X in earnings is higher in one case than in the other. (Retained earnings could explain a minimal part of the increase.)
There is no reason for that $100bn company to be a $110bn company next year if it has returned the $10bn it earned to shareholders and it's still going to earn $10bn.