What is the "beginning" you refer to in your question?

I think a better formulation would be: "At what point did Julius Caesar decide to make himself dictator in perpetuity and why?"

Just to clarify, considering that "Dictator" was a special magistracy in the Republic that one had to be elected to, and as there was no precedent for one being elected dictator in perpetuum (dictator for life) as Caesar eventually was, are you asking whether or not Caesar intended to become rex (king) or princeps (emperor)? Or whether he specifically intended to be elected to the position of dictator, and perhaps given permanent legislative powers? Because I would suggest that there being no precedent for such a thing, the latter was an impossible political goal. Perhaps the question could be phrased most accurately as "did Caesar plan to supplant Pompey as the leading man in Rome or was his hand forced?" Is this an accurate paraphrasis?