Iceman isn't my area of expertise, but I'll answer as best I know. His freeze ray lowers the temperature of things and causes ice to form around them as a rule. He doesn't normally cause explosions or craters as this is almost the opposite of what he's doing (which is reducing the kinetic and thermal energy of his target). He can throw ice as projectiles, which would cause impact craters but not explosions.
I think they ended up doing that because they needed to drag the episodes out as long as possible. They caught up to the newer manga too quickly and didnt want to make a bunch of filler episodes like what happened with Naruto for a while there.