This is partly in response to the frightful traffic situation on I-35 through Austin, among the worst in the nation.
Texas 130 was built in part to give through traffic, especially truckers travelling to/from south Texas (to whom time is money) a way of avoiding Austin. But the tolls are substantial.
Increasing the speed means decreasing the time, and thus the additional time saved will (in theory) make it a financial win for more truckers to use Tx-130.