Again, When in the last round, Ashok was against punishing the imaginary Mother(who killed her criminal son), Chanakya took Sushim's side and made him win. Although, he just supported what was right, it is also true that Chanakya can easily prove right as wrong and wrong as right with his tricky words. But he again chose not to help Ashok.
These incidents indicates that Chanakya wanted Sushim to win. The reason may be that Ashok's abilities are already proven and there is no need to further prove it. Now its time for Sushim to prove his disability. Chanakya knows very well that Sushim, after becoming the temporary king, will definitely display his cruelty and his inefficiency thus making Ashok's way to throne more easier.