Eli5: Why was it world-changing that Caesar crossed the Rubicon?

Question

Eli5: Why was it world-changing that Caesar crossed the Rubicon?

In: 1397

Answer 1

slight tack on since i did not see it mentioned… the crossing of the rubicon also included Big C burning the bridge behind him, and became the source of the saying about being careful about burning bridges, as if his gambit failed he had no retreat.