A diplomat is someone appointed by a state to conduct a dialogue with one or more other states or international organizations. The main functions of a diplomat are to: represent and protect the interests and nationals of the sending state, beginning, and facilitation of strategic agreements, treaties, promotion of information, trade and commerce, technology, and friendly relations.
One of the main roles of the president is to be the chief diplomat. That being said, Trump is a diplomat. For example, Trump and Israeli prime minister have similar worldviews and in public, seem genuinely excited to be working together. Trump seems genuinely interested in brokering peace within the Israeli-Palestine conflict. Trump seems to be making his own rules as a diplomat.
One thing that you can say about Donald Trump is that he is one accidental Diplomat. He had decisions that made him completely erratic and people did not understand his actions very well. It seems that this has made him a bit scary for the leaders of other parts of the world. They know that it will not take long before he starts a war if things do not go his way.
Whether his actions are meant to be strategies in order to let the people make peace or he simply does not know what he is doing, people will never know. What matters is that he was able to become a diplomat and he managed to make some changes that will impact the rest of the world.