In Texas the A.G. doesn't prosecute cases unless he is helping a local prosecutor or (at their request) or appointed because a local prosecutor has a conflict. Even if Abbott finds evidence to support a case he still needs an elected prosecutor in the proper jurisdiction to take the case to a grand jury.
Earle is the Travis County (Austin) DA. The Travis County DA gets part of his funding from the State of Texas and is charged investigating and prosecuting certain public corruption cases. As a private citizen dealing with an out of state corporation Burkett doesn't come under Earle's purview.