I’m pretty sure Trump had no idea who the hell this guy was before he walked into the Saudi embassy a few weeks ago.
#1 Khashoggi was NOT a 'journalist'. He was a 'mover & shaker' in Saudi Arabia, the nephew of mega-arms dealer Adnan Khashoggi and a Muslim Brotherhood promoter who happened to write a few articles for the WaPo. He has been labeled a 'journalist' by the MSM to ensure widespread sympathy in and coverage by every news media outlet on the globe.
#2 You can be sure that he was known to the US intelligence community, White Hats & Black Hats. If necessary, Pres. Trump had been briefed on his activities before he 'sauntered' into the Saudi Embassy to get his paperwork to marry a Turk.
..or anyone else who doesn't run in those circles. I'm still trying to figure out why this guy is important.