Given DGR is the holding company of DHR and DGR is spawning...

Given DGR is the holding company of DHR and DGR is spawning heaps of potentially great businesses across a wide range of resources...

Apologies if this is a silly question but why wouldn't I want to hold DGR instead of DHR as a way to back the apparently excellent management of Nick Mather?

Shouldn't DGR, as parent company spinning out these great resource businesses be more profitable over time than the companies it spawns?

I'm asking cause I'm seeking to understand the capital structure better.

If DGR is such a great business model generating ridiculous amounts of value, why is the SP so up and down?

Note: currently a holder of DHR.