The current assessments of George H.W. Bush's life often include a statement to the effect that in the past the elite, as exemplified by Bush,, used to believe in service to the nation, in noblesse oblige. Such statements seem to be accepted unthinkingly, without question.
I'm not so sure there's that much difference between now and the past. When you look at the business elite, the big shots with the big bucks, there seems to be a mixture of plutocracy and service. For every Rockefeller, Ford, and Carnegie Foundation created decades ago you can match similar efforts by Gates and Buffett.
Charlie Wilson famously said what's good for the U.S. is good for General Motors, and vice versa. Our current elite knows better to say that, but I suspect they think it. Wilson headed DOD under Ike. Trump has had his own set of rich men, members of the elite albeit rather second level, serving in his administration.
My bottom line is that there's always been a mixture of motivations for public service: some people want new fields to explore (think Sen. Corker), some people want a career in politics moving in and out of government depending on which party is in control, some just fall into it.
[Update: Erik Loomis at Lawyers, Guns, & Money visits the
grave of Joseph Choate, touching on some of the good and bad aspects of the old-time elite beliefs. Choate's brother founded the Choate private school, now
Choate-Rosemary Hall, attended by many elite, including JFK. ]