He didn't just steal content. He then tried to blackmail the company to not release the content he stole.

Also, while you might be able to justify piracy of a released product in various ways (the common argument is that the would be pirate wouldn't have paid for the product anyway and digital goods don't have any cost to the developer from pirating them). But when the product hasn't been released yet, then it has a much bigger cost because the pirated copy is the only option available and thus it can eat into actual sales. The inability to go through with their planned launch (something big publishers will spend millions hyping) and the release of an unfinished product can absolutely have financial damages. It's hard to recover from a bad launch.

And that's without getting into the fact that hackers like this don't usually stop at just leaking video games or the likes. They'll also often steal people's personal information. It's a lot easier to see the moral issues when it's your information being stolen.