Hola Alejandro

This structure using "lo que" is idiomatic, we can't really translate literally or at least it looses meaning if we do. We don't use just "que" for this purpose. I'm not sure what your doubt is exactly in terms of "lo que" vs "que" in this context as "que" as I said is not used.

"Que" can be used in many other different ways, as a conjunction, as a relative, to express disbelief, a cause, a warning... but not in this specific structure to express surprise/emphasis. 

If you go to your dashboard and use the search box on the top right corner, you can type "using que" and "using lo que" and lots of different lessons will come up for specific uses of those. 

Saludos

Inma