I'm going to guess that it had something to do with Bragg and/or Dick Taylor.
Taylor was passing through Chattanooga at the very time of this message from Bragg to Van Dorn about the latter losing Villepigue.
In his "Destruction and Reconstruction", Taylor speaks of his meeting with Bragg in Chattanooga. Taylor says that Bragg had requested the War Dept to assign Taylor as Bragg's chief of staff.
The footnotes quote President Davis' letter of Aug 5, 1862, to Bragg that "Gen Taylor seemed to be required for SW Louisiana...."He appreciated the compliment of your request that he should be sent to you as a division commanders."
As usual, doesn't sound like the right hand knew too much about what the left hand was doing. The President says Taylor seemed to be required, Taylor thinks Bragg wants him as chief of staff, Davis thinks Bragg wanted him as a division cdr, etc.
Perhaps a fair assumption would be that Bragg wanted to substitute Villepigue [with his French heritage?] in Louisiana for Dick Taylor, so that he could keep Taylor for himself.
Taylor eventually crossed the Mississippi River on August 19, 1862.