This is not running it as root (i.e. privileged userland, still ring 3), this is running it as ring 0 (i.e. the level that the kernel runs at, with no restrictions on access to memory and hardware at all). A tiny bug in ring 0 code can take down the system or open security vulnerabilities, where the kernel can provide more hardening to protect applications to an extent.

You could say this is the inner circle of hell.