Why did Napoleon overthrow the Directory?

The Directory was a five-man committee that took power in France after the fall of Robespierre. Its immediate aim was to restore some semblance of order to a country wracked by the widespread chaos and bloodshed of the Terror. Although initially quite successful, the Directory soon ran into serious difficulties. Conflicts continued apace, with large parts of the country in open rebellion against the government in Paris. The economic problems bequeathed by the Jacobins spiraled out of control—unemployment and inflation soared. France was on the brink of bankruptcy. All the ingredients for another Revolution seemed at hand.
Meanwhile, Napoleon was continuing to prove himself a highly skillful general on the battlefield. His military successes merely served to confirm Napoleon's egomaniacal tendencies, his implacable belief in his own ability. France was rapidly degenerating into chaos, and Napoleon passionately believed that he, and he alone, was the man to restore order and stability.
Fortunately for Napoleon, many in the upper echelons of French politics felt the same way. Behind the scenes, Napoleon and his allies set to work by trying to ease him into power. A fictitious Jacobin plot was fabricated to provide a pretext for Napoleon to take control. Unfortunately, the plot did not go according to plan. Napoleon's allies squabbled among themselves, and when the Corsican general lost patience and tried to force the issue, he was sent packing by an angry, restive Council of Elders.
Enter Napoleon's brother Lucien to save the day. He harangued the soldiers guarding the Assembly, convincing them that there were traitors inside in the pay of England, hell-bent on assassinating Napoleon. After a long search, a sufficient number of deputies was found to authorize the establishment of a triumvirate, a government consisting of three Consuls, one of whom would be Napoleon. This was an attempt to try and give the coup (for that is essentially what it was) some degree of legitimacy. However, there is little doubt that the new regime was formed more or less at the point of a bayonet.
Although power was formally split between three men, there was little doubt as to who was really in charge. The two other Consuls, the Abbe Sieyés and Ducos seriously underestimated Napoleon. As he continued to rack up an impressive string of military victories, he steadily began to consolidate his dominant position within the Consulate until he became First Consul, with full executive power, in December 1799. Napoleon's power further increased until, in 1804, he consolidated his position by crowning himself Emperor.
https://www.ngv.vic.gov.au/napoleon/revolution-to-empire/the-rise-of-napoleon.html