Jesus had given the disciples the power to heal
the sick and cast out demons and apparently they
had been successful. So they figured they could
also heal this boy.

To their surprise they were not able to cast the
epileptic demon out. The evil spirit threw the
boy to the ground and refused to come out,

The scribes were excited over the disappointed
disciples and more than likely took advantage of
their failure to disgrace them in the eyes of the
crowd.