They embrace the institutions because they know exactly how much they control it. In this sense Trump's politics realy doesn't do much for them and lacks any appeal.

There is a fair bit of reactionary tribalism. They don't want Trump and his clearly less "refined" clan encroaching in their circles, they certainly couldn't give a shit about the current MAGA base. The (70-80s) Reagan era is quite literally the turning point of the greatest attack on the American working class since WW2.

Meanwhile MAGA at least pretends to care about working class whites. Of course in the end Trump comes through with massive advantages for the richest capitalists(literally bigger tax cuts than Bush) too, but in the end I guess that "populist" optics is just too much.