Trump has been encouraging SA to invest heavily in US and his family have strong business links.
There were also numerous countries that didn’t support the U.S. in their war against Iran due to political/ legal concerns. I think it’s more than a personal grudge by the Donald
I liked the following explanation-
“The US has participated in the Yemen conflict in the past. It reached an understanding with the Houthis in 2025, under which it stopped its bombing campaign in return for a Houthi commitment not to attack American vessels.
That arrangement is still relevant. Right now, the Houthis are threatening only Saudi ships in the Red Sea, but they have the power to completely disrupt navigation in this crucial water body. With the world still reeling from the economic shock of the blocked Strait of Hormuz, the US would not want this.
Also, US munitions are running low as the war with Iran grinds on.
The Trump administration would not want to open another front in the Middle East when midterm elections are approaching and the Iran war is anyway unpopular.“
https://indianexpress.com/article/explained/explained-global/saudi-arabia-defence-pact-pakistan-turkey-us-houthis-10882946/
So U.S. don’t want their own ships bombed, their munitions are running low and it won’t play well to the electorate prior midterms. Shows what a precarious position even the U.S. are in.