> Applets were executed completely outside of the browser sandbox. An absolute disaster from the security standpoint.

It is easy to forget Java (applets, web start) was a thing during the Windows 98 era, meaning a time when there was (almost?) no security. People were downloading and running random .exe files all the time.

There was no browser sandboxing and you could run wild Basic code in IE.

Sun with Java were the first one to try to solve that problem. It was imperfect but way better than what others were doing at the time.