When Barack Obama became president, George W. Bush followed the tradition of past presidents of remaining silent and allowing the new president to govern without becoming a critic of their policies.
It's a good tradition that reaffirms America's democracy and the peaceful transfer of power. But, apparently Barack Obama has already said that he will become a vocal critic of the Trump administration. Lord knows Bush had plenty to say of the shambles Barack Obama has made of America. But, he followed tradition and kept his mouth shut.
I guess Barack Obama doesn't Bush's class.