The economy of Texas in the middle of the nineteenth century was less developed than that of most other states, and therefore less dependent on slavery. This made it easier for Texas to adapt to the situation after emancipation, since the population of freed slaves was smaller, and neither the economy nor political organization was so severely affected. The white population was also more mobile and dynamic, as people were continually moving West to farm and develop land that had previously been wild.
In terms of both politics and geography, Texas was only ever loosely part of the Confederacy. Most of the fighting took place further East, meaning that the physical effects of war were less marked in Texas. Texans were also less attached to the Confederacy as an idea. This meant that they were less psychologically affected by the loss of the war, and less prejudiced against Yankees when it came to doing business and cooperating politically.
Texas quickly developed its own identity as "the Lone Star state," and its political leaders did not continue to regard themselves as part of the defeated South. In other Southern states, white supremacist leaders spent decades fighting against the effects of emancipation and refusing to work with politicians and business leaders from the North. It is scarcely surprising that the Northerners preferred to do business with more dynamic Texans than with Southerners who continued to view them with resentment.