microwaves are wild. the waves are polar and so are water molecules. the crest and trough of the wave are basically opposites ends of a magnet, so when they smash through your hot pocket at the speed of light, all the water molecules in the hot pocket are spinning back and forth from the magnets on the waves buzzing through. and the water molecules are spinning so fast it gets real hot, and gets hot from the inside.
ovens just turn the heater on real high. so the air has to get hot then the outside of the food can get hot and then eventually the inside of the food. slow.