During a conversation moderated by Mr. Schwarzman on Tuesday, Mr. Kushner praised the work of Mr. Trump and talked up his re-election prospects.

“What we’re finding is that the enthusiasm for the president right now at home is stronger than it’s ever been,” he said.

The larger crowd this year led to sold-out hotels and gridlock across Riyadh, as cars and coach buses descended on the gated compound of the Ritz. But it appeared that even those who skipped last year’s conference never really left the kingdom.

“I have a lot of clients here in Saudi Arabia and I am of a big belief, from a political perspective, that I don’t get involved with other countries’ politics,” said Anthony Scaramucci, the founder of SkyBridge Capital and former White House communications director.

Mr. Scaramucci sent members of his team last year, but did not personally attend because he was on a book tour.

“I recognized that a lot of people decided not to come, but my team elected to come because we have longstanding relationships with Saudi Arabia,” Mr. Scaramucci said in an interview outside the Ritz’s main ballroom.

Others that scorned Saudi Arabia last year re-emerged. The chief executive of Virgin Hyperloop One, a futuristic transportation start-up, closely associated with Richard Branson, the British entrepreneur, pulled out last year after Mr. Branson criticized the kingdom and suspended two projects he was working on there. This year, however, Virgin Hyperloop One was back and even installed a jumbotron-style display of the project outside the main conference hall.