My guess either (1) he realizes the Lefties have won the war already, so no sense rocking the boat... or (2) Odumbo has some dirt on Romney that he didn't want made public.
They all want to feel like they are elite, above common ordinary people who need to hear what they have to say before they know what they should do. Trump bypasses them all and goes straight to the people and makes them look like old losers. Some poor journalist finally quit her stupid job at People Magazine and got a job at the Washington Post to finally cover serious politics, and now she is really confused.
He went by the same playbook McCain used, one written by loser campaign consultants. Be positive, don't criticize the minority guy, play to the media, don't say anything controversial. Meanwhile the Obama campaign was accusing Romney of murdering a guy's wife. No apologies. Harry Reid said Romney had cheated on his taxes, no proof and none asked for by the media. Trump is following a somewhat different strategy.
no kidding, they first opined nobdody could say that and get away with it in the media. Now they all realize you don't even need the media (as long as you can get them to say something about you.)