More the magnitude of randomness in the total vs "ordered" growth. A truly random stock market would imply an utterly insane economy (avoiding the obvious jokes for now). A company with good current and future prospects that everyone knows going down over time continually while a doomed one rises? One at a time maybe from "glitches" or extreme circumstances. Like say a massive need for short term funds and more ending shorting than available shares to cover it and a margin call chain for the latter. Both at once? Likely impossible even with extremely weird economic circumstances which make the COVID-19 economy look perfectly normal.