That's a good question. Sand is a component of soil but, as we know, wet sand doesn't turn into soil, so water being removed isn't enough to turn soil into sand. Apparently essential nutrients must be leached from the soil thru soil erosion AWA lack of rain.

Lots of articles on turning sand into soil, here's 1 that explains how deserts form & how to reverse process:

We Can Turn the Desert Back Into a Fertile Land
These easy techniques can help retain rainwater and reduce soil erosion.
The Sahelian region is affected by strong winds and low and erratic rainfall.
That contributes to soil erosion and degradation, nutrient depletion, and poor fertility.

https://medium.com/illumin...

Oklahoma was turned into a Dust Bowl in the 1930s by combination of poor farming habits & drought, resulting in the fertile top soil being blown away.

The Encyclopedia of Oklahoma History and Culture
DUST BOWL.
The Dust Bowl period that occurred during the drought years of the 1930s represents a remarkable era in the settlement history of the West. From a climatic perspective, the 1930s drought is still considered to be the most severe on record for many parts of the Great Plains.
[...]
From 1909 to 1929 farmers had broken out thirty-two million acres of sod in the Great Plains. Many of these farmers were recent settlers and had limited experience with the region's climate. Once the protective cover of the native grassland was destroyed, the dry conditions and high winds common to the region resulted in an increased susceptibility of the topsoil to wind erosion.

https://www.okhistory.org/...