The exact reason has not been mentioned.
I think the reason for multiple orbits to reach lunar transfer orbit may be due to inadequate deep space information. Calibration of the deep space network data may be one of the reasons. This will allow future lunar injections to be more precise.It will also allow a greater margin for any error during lunar capture compared to a direct lunar orbit transfer with a single lunar injection.The original diagram at the isro website called for a LEO, GTO and then a firing via a Hohmann transfer orbit with midcourse correction to reach lunar capture followed by recorrection. That may have a lower margin of error. also this will not give sufficient tracking and calibration data of the new Indian deep space network.