By crossing the Rubicon with his one legion, Caesar put himself on a path of no return and in open conflict with the Senate and Pompey who vastly outnumbered him military. There was no guarantee that he would succeed. Upon crossing he declared "alea iacta est", knowing full well what he set in motion. Edit: My point here, is simply that not everyone would cross the Rubicon. Most would turn around, deeming the risk too high. Related to a startup, the risk for failure is high if you look at the statistics. If it is a "sure thing" you are not really doing a startup or you are conned. A startup kind of by definition has to be a high risk venture. Like PG's example of a merchant ship going to the East Indias in the 17th century.
I don't think he intended or expected that the Boni would essentially force him to wage a war of total victory against them.
Bringing legions to Rome as part of political struggle had already been common practice for centuries, but it had never fully destroyed the Republic. Caesar himself witnessed several such occasions by Sulla and Marius.
Edit: responding to edit, my point is that Caesar was not fighting to gain. "Crossing the Rubicon" means taking a risk, but I don't think using it to describe creating a startup really fits.
He was fighting (illegally, it might be added) to defend himself against the political tactics of his Senatorial opponents. While he held an Imperium he could not be brought into court for his actions in holding it, but the Senate had voted to make him lay it down. Their intention was to bring him to the courts and ruin him politically and financially. Caesar was simply too proud and too arrogant to allow that ruin; that he was the foremost general of his age meant that he was in a position to pull it off.
Who knows? I believe you are right that he was forced into action when the Senate pulled him back from Gaul [1] with the intention of bringing him to court. If he did not have a plan to set himself up as a dictator, at least he pivoted beautifully once he saw the opportunity and Pompey folded. That at least was a true startup move. 1. edit: Gaul not Germany
