The reason is much more basic than that, and already said by Hillary Clinton--Trump lacks the temperament needed to function properly as President.
It's as simple as that...
Not so he behaves in a very controlled manner. When people in the political field hit out at him he hits back at them in the same way. When they make peace with him he makes peace with them. Leaders of other countries will understand very quickly that he'll make sure its against their interest to provoke him. People don't get to be government leaders without understanding their self interest.
They'll all learn quickly not to say anything that provokes him. No world leader will say anything to provoke him, four years of peace. Contrast that with the continuation of endless wars and bickering with Russia and other countries Hillary is likely to get involved with, Trump seems like the safer option.
I disagree.
His attacks on Machado and Clinton last week were unprovoked.
He had the chance to take back the words and stop the tirades, but he never did.I'm not sure how you can say that the attacks on Machado and Clinton were 'unprovoked'. They both attacked his character so he attacked theirs. If they hadn't had a go at him he wouldn't have had a go at them.
What 'bluff'? If someone hits him they can be sure he will retaliate proportionately. That's what he always does.