User blog comment:Ale-Alejandro/Ale's Complaints About TD:ROTI/@comment-2142545-20120414182502/@comment-2142545-20120415194214

Actually, Two reasons from the 2011 fan expo. Potenza said that after TDWT became a hit- and that it was their best season ever, the writers wondered. "Where do we go from here?" So they tried new characters and 13 eps. Also, the 13 eps came from Cartoon Network not wanting to pay for 26 eps. So that's also what happened.