Most modern U.S. presidents (of both parties) have promoted democracy around the world -- and part of that was support for a free and unfettered press in every country. Donald Trump has done just the opposite. While criticizing our democratic allies, he has demonstrated a fawning respect for dictators around the world. And he has demonized the free press as an "enemy of the people".
Saudi Arabia (one of the world's most undemocratic countries) saw this, and it encouraged them to murder a journalist who exposed their shortcomings. They knew that could do this with no retaliation from the Trump administration. In my opinion, that means Trump has some of the blood from the slain journalist on his hands.
Here is how Brian Klaas describes it in an op-ed for The Washington Post: