Coworker quit by hitting the resign button in workday

I worked with a coworker for about 4 years at a company I used to work for, he was my work bestie because he was the only one in my office that played video games like me. There was a big transition earlier this year when a competitor bought our whole division in June. I went to work for the competitor after the transition but my coworker stayed in a different and completely different role. I grabbed lunch with him last week and found out he had quit two weeks earlier because he was super stressed and the role wasn’t a good fit.

I’ve been trying to get him to come over to the new company because it’s a similar role to what we had but better in every way, but found out through my team lead who is still in contact with the old company, that my coworker quit by hitting the resign button in workday. No email, no call to his manager, did not notify anyone. He just woke up one morning and clicked the resign button in workday and stopped working. This was a company he worked for for over 4 years, Fortune 500 career job, and quit without notice or had anything lined up. Hr was calling him repeatedly for 2 days wondering if he was ok, because they obviously thought the workday button was a mistake because who even does that? Makes me even hesitant to refer him to my company if he’s pulling bs like that.

I thought it was crazy when I found out earlier today, who would do that, especially in this economy and job market?