But it wasn't a human computer. It was a trisolarian computer made up of trisolarians that were alien beings that had the ability to do things like hyper-fast communication and always be truthful. Both of those traits could actually make for a viable computer system whereas humans obviously would not. I can see how you may have thought that though because in the 3 body problem simulation "game" in the book the trisolarians are represented as humans (the author does point out the difference though)

On a side note, is our system of government really all that different from a mass human computer?