The one with Constantinople is BS, the gate that was left open wasnt a major gate as he claims, its was a small gate leading to the wall which made it possible for Turkish troops to raise the flag on the top of the wall, it wasnt the reason for success of penetrating the defense either, more like a catalyst since there were several breaches in the wall already according to historians.
Shortly after midnight on May 29 the all-out offensive began. The Christian troops of the Ottoman Empire attacked first, followed by the successive waves of the irregular azaps, who were poorly trained and equipped, and Anatolians who focused on a section of the Blachernae walls in the northwest part of the city, which had been damaged by the cannon. This section of the walls had been built earlier, in the eleventh century, and was much weaker. The Anatolians managed to breach this section of walls and entered the city but were just as quickly pushed back by the defenders. Finally, as the battle was continuing, the last wave, consisting of elite Janissaries, attacked the city walls. The Genoese general in charge of the land troops,[3][55][56] Giovanni Giustiniani, was grievously wounded during the attack, and his evacuation from the ramparts caused a panic in the ranks of the defenders.[83] Giustiniani was carried to Chios, where he succumbed to his wounds a few days later.
With Giustiniani's Genoese troops retreating into the city and towards the harbor, Constantine and his men, now left to their own devices, kept fighting and managed to successfully hold off the Janissaries for a while, but eventually they could not stop them from entering the city. The defenders were also being overwhelmed at several points in Constantine's section. When Turkish flags were seen flying above a small postern gate, the Kerkoporta, which was left open, panic ensued, and the defense collapsed, as Janissary soldiers, led by Ulubatlı Hasan pressed forward. Many Greek soldiers ran back home to protect their families, the Venetians ran over to their ships, and a few of the Genoese got over to Galata.