Well for starters,  King Salman met Trump when he arrived. Didn't do that with Obama.  I'll bet when he goes to China, they'll roll out the red carpet too.  With Obama, they not only didn't roll out the red carpet, they didn't provide him with the stairs to deplane Air Force One.  He had to exit through the back door.

In addition, King Salman shook Melania's hand.  The royalty there never does that with women.  He was not only showing respect to our First Lady, but more importantly to Trump.