You are not just voting for him, you are voting for the people he knows and could bring into an administration.
Your talking about "shadow cabinets" or "shadow government" (its just a phrase, it does not mean anything negative). The concept is more common in parlimentary democracies, though I have always wished to see it brought to the US in terms of campaigns.
Though the possibility is slim, it allows a candidate to many targets to hit and to many vulnerablities to attack. I.E. run mud slinging campaigns on everybody to drag down the initial candidate.
ALL “think tanks” play “shadow government”. That’s the sole purpose of a “think tank”...