If your bear case is a 10-year recovery to 40 from 20 that's a CAGR of 7.18%, about the same as the long-term average CAGR of the S&P. The difference is that the S&P doesn't have bankrupty risk, whereas airlines do [1]. So on a risk-adjusted basis, that kind of trade isn't too appealing unless you'd done significant research to show that the risk of bankruptcy or a buyout by a competitor at a reduced valuation was unlikely.

While you might have done that kind of research, the article implies (correctly, in my view) that the typical Robinhood user did not. No surprise; that sort of research is time consuming and requires significant familiarity with the industry. Yet airlines, cruise companies, and other risky assets were preferred by Robinhood users throughout the pandemic.

[1] https://en.wikipedia.org/wiki/List_of_airline_bankruptcies_i.... These lists omit airlines that get bought up for pennies on the dollar by competitors.