So is Trump right to be reversing the tone and message of his predecessor?

In the short term, probably. At the very least, reassuring Arab Gulf states that the United States stands behind them against Iran in particular could discourage unhelpful behavior and might even allow the Saudis and others to wind down the campaign in Yemen. Additionally, neither Trump nor his voters might like the Saudis all that much, but Saudi Arabia remains vitally important to the direction of both the region and other Muslim-majority states. I tend to buy the Emirati argument that although the United States doesn’t want to get caught up in any Saudi royal succession drama, we do have an interest in the aggressive reforms proposed by Mohamed bin Salman at least partially succeeding. Saudi Arabia cannot continue on its current course, and a more socially tolerant, economically diverse Saudi Arabia is in everyone’s interest. So if U.S. Crown Prince Jared Kushner and Saudi Deputy Crown Prince Mohamed bin Salman are now BFFs, well, great.

In the long term, though, the Arab states have to understand that America will not be in the region forever—at least not in today’s numbers. We have interests elsewhere, and finite resources to protect those interests. Also, putting it bluntly, ensuring Gulf hydrocarbon resources make their way to the market is less of a priority for the United States today than it was three decades ago.