I think it was pig headiness, trying to show he's the boss of the Wold and a itchy tweeter finger (he can't wait to get back to the US and tweet how great he was). He did a smaller thing at the last G7 and he left the last North Korea meeting early. He has said some of the meetings weren't worth his time but I don't think it's his time its the American peoples time because they are paying for these meetings and they should get the full package not just want Trump wants to attend. Cheers!
They treat him like a hissy fitty tantrum-at-any-time loose cannon ready to explode. They know he is spoiled rotten and loves to be a**-kissed so they kiss his corpulent butt but expect only to contain him from doing damage. They will do whatever it takes including complimenting to make him think he is rspected valued and important. He is none of those things. They have his number. He has no clue. Thank you for your reply Nanoose! :)