Which two moves in the Battle of Actium were most important to Octavian's victory and why?

Octavian used small battleships, which enabled him better maneuver and one of Antony's commanders escaped Octavian and revealed to him Antony's war plans.

Explanation:

The battle took place not far from the Greek coast, at the entrance to the strategically important Bay. The bay covers as much as 50,000 hectares of sea surface and is separated by a narrow passage just 580 meters wide from the Ionian Sea. On the promontory at the entrance to this passage is the ancient city of Actium. Octavian's fleet commanded the aforementioned battle of Marco Agrippa, known for his later great construction efforts in Rome (he also became Octavian's son-in-law). Octavian's fleet contained about 250 warships, most of them smaller Liburnian ships. Marcus Antony's fleet was more numerous and consisted of typical Roman quadriems and quinquems (ships with 4 or 5 rows of oars) and large war galleys, the largest of which had as many as 10 rows of oars. Although very resilient and powerful, Antony's ships could not maneuver well. Their crews were decimated by disease, while Octavian sailors were healthy and experienced. Furthermore, one of Antony's commanders escaped Octavian and revealed Antony's war plans to him. Cleopatra's fleet with large Egyptian war galleys was just beyond the center of the battle, and it fled shortly after it began toward the high seas. The reason for this is still unknown Panic spread among the ships of Marc Antony and they were defeated relatively quickly. After losing the fleet, she left Mark Antony and his ground army, which, on the eve of the battle, was practically as strong as Octavian's.