Was it purely coincidence? Would the French have begun to win back territories by that time in the war anyway? Did Joan have some prior knowledge of tactics?
Long story short, they barely listened to her. Former answer on the same topic Other answer, on the same topic, but with magic.
The English were already in a tough spot at Orleans. Their major military commander died at the beginning of the siege--which meant the men loyal to him went back to England. The Anglo-Burgundian alliance was also in tatters, so much that the Burgundians left the siege at Orleans, leaving only a few English fortified but isolated strongholds around the city.
When Joan arrived, most of the best and daring French military commanders had gathered at Orleans. She was left in the dark of the operations. She barely made it to her first battle for she wasn't warned it'd happen. She was wounded, a few days later, yet her standard served as a rallying point and an English stronghold fell which liberated the city's south entrance. Joan was therefore seen as a prophetess of some sort from that point onward.
A few months ago, she was mistaken for a healer by the Duke of Lorraine. She told him to stop cheating on his wife and she asked if his son-in-law, the young Duke of Anjou, could accompany her to Chinon. That request was denied.
Healers, preachers, holy men and devout women were not unusual at the time. They roamed the country, never staying too long in any city. Joan could have become such an individual but she was headstrong set on achieving her mission: to drive the English out of France.
When she died, the war was far from over. The real turning point came in 1435 when Philip the Good, Duke of Burgundy, had his way with Charles VII and reconciled with him, securing his own authority on vast chunks of land he gained prior by allying with the English. Even then, Charles VII only recovered Normandy and Gascony twenty years after Joan's demise. At which point she'd been forgotten or replaced. A woman even pretended to be her at some point and lived her own little adventure.
Also, before Henry V revived the Hundred Years War in 1415, it came very close to an end when Charles V and Richard II almost buried the hatchet with a wedding. However, one turned crazy and the other was deposed.
Joan showed up at the right time with the right mystical God-sent message. However she barely achieved anything by herself. She wasn't well-received by most of the French military commanders but she made a terrible impact on the enemy. The English were dead-scared of her and the Burgundians (who were French) believed she could master witchcraft. People were divided about Joan, she didn't know what to think of her.
When she bossed the Bastard of Orleans around, declaring she benefited from a better council than he did for she was given informations by saints in heaven and by God through them, he sure didn't know what to make of her. When the commander in chief of the French army met her, he wondered if she was from the devil or from God but he stated that he didn't care for he didn't fear her. His own mother had been tried for witchcraft so... he would have known.
The best explanation is that these were crazy times and as for Joan, timing was everything. She built up quite the charisma but mostly she intrigued everybody who met her.
This was answered pretty well by u/sunagainstgold in a different thread 2 years ago