How can retail investors who started investing only after March 23 2020, afford to invest?

I read this Money SE answer that cites No, The Market Is Not Rallying Because Of Robinhood Traders, Barclays Says

Key background

A wave of new retail investors piled into zero-cost brokers like Robinhood, Charles Schwab and TD Ameritrade as the market hit a coronavirus recession low point on March 23. Robinhood, for instance, saw a historic 3 million new accounts added on its platform during the first quarter, as stocks plunged in the fastest bear market on record. Barclays’ analysis uses data from Robintrack, a separate platform which tracks the number of Robinhood users holding a stock over time.

The CARES Act’s $1200/mo. isn’t that much money. Obviously, many Americans are unemployed and/or have had to line up at food banks. I don’t think they can borrow that effortlessly, when millions of credit card users are seeing their cards closed or limits lowered during pandemic.