Sysadmin sank IBM Mainframe by not going one VM deep enough
The article's headline got it wrong.
Don't say the "Sysadmin sank IBM mainframe by going one VM too deep"
The problem isn't that he went one VM too deep. It's that he went one VM too shallow. He killed the first, top level VM.
If he killed the second level VM, it would have taken its children along with it, but left the top level alone.
The headline could read, "Sysadmin sank IBM Mainframe by not going one VM deep enough."