**Also posted in Meta but sharing here too. Even if it helps one person it’s worth it**
How exactly was he hacked? Even I myself shows publicly my email address, yet encountered no issues of hacking nor anything so far. Maybe he had entered it in a website where they had data breach, or his password wasn't that kinda strong. There can be alot of prevention that can be done by BitcoinGirl.Club in his ends.
There can be many options, but the fastest way that comes to mind is that a virus has been caught. A virus that steals browser logs. And since most likely the owner had one browser, which he often used, and did not erase cookies after each session, all the logs were transferred to the hacker.
A lot of information can be stored in one log. Starting from location data, and computer processor, and ending with passwords for mails, forums, bank cards. If a keylogger was installed in the system, then everything that the owner of the browser pressed was available to the hacker.
How to avoid such viruses, I think everyone has long understood, do not download anything from the Internet, use antivirus software, and other protections. You also need to erase all your cookies after each session and use different browser profiles for different tasks.
After such a data theft situation, you need to reinstall the operating system. Or reinstall the browser again.