Corrected entry: Callahan had obviously been planning his revenge for a long time, and the microbots were a huge part of the revenge. But if Hiro hadn't invented the microbots, then the entire movie wouldn't have existed. So Callahan basically just was lucky that a kid invented these amazing things, that were somehow just perfect to get revenge.
TheCleverGal
3rd May 2016
Correction: Callahan was plotting his revenge and got lucky when Hiro showed up with his microbots. He saw the advantage they gave and plotted to steal them, faking his death in the process. It's not a plot hole, it is just the plot. If the microbots weren't available he would have used some other technology.