Kearns may not have realized that his negative cash balance displaying on his Robinhood homescreen was only temporary and would be corrected once the underlying stock was credited to his account. Indeed it’s not uncommon for cash and buying power to display negative after the first half of options are processed but before the second options are exercised—even if the portfolio remains positive.
“Tragically, I don’t even think he made that big of a mistake. This is an interface issue, they have slick interfaces."
I think this is the saddest part. This definitely is entirely Robinhood's fault. Saying so is basically saying a casino is at fault for somebody committing suicide because of a gambling loss. But a better UX could have helped in this case.