Perhaps the one thing the crusaders in 1204 feared was the population of Constantinople.

Perhaps the one thing the crusaders in 1204 feared was the population of Constantinople. “As strange as it may seem, the people of Constantinople wanted nothing to do with fighting the Latins.” Why did they not try harder to save themselves?

The day before Constantinople would be firmly in the clutches of its enemy, the Crusaders had already entered the City. However, they were hesitant to go forth into the city during the night: 

“As the sun sank the various groups of Latins assembled in the burned region for a general parliament. The leaders spoke to the army of their dangerous situation. Constantinople, they believed, still had for more men under arms than did the Latins.” They knew if the hundreds of thousands of civilians armed themselves and fought - it would be a huge challenge. “No one believed that Constantinople was taken, nor that it could be taken very soon. Villheardoin states bluntly that even a month would be insufficient to conquer so large a city. The massive population, narrow streets, and dense buildings suggested brutal house to house fighting, which the Franks abhorred. They feared that should their troops venture into the city’s snarl of backstreets and broad avenues they would easily be picked off by lone assassins, tumultuous mobs, or residents throwing down roof tiles. They, therefore, forbade the army to seek quarters in the city.”

They expected a huge fight, and according to Villehardouin they were prepared to set more fires to burn the Romans out if needed. “Altogether the fires had turned one-sixth of Constantinople into smoldering ruins and eliminated perhaps one third of her dwellings.” Much of the city was “charred wastelands” by the time the city fell. 

The Emperor, which changed many times, only had around 6,000 Varangians in terms of high quality troops. However, there were lesser troops and most importantly the potential militia drawn from the people of Constantinople. They were a deciding factor in the battle. “Like the crusade leaders, the emperor realized that the massive and destructive mobs could overwhelm the Latins if they so chose.”

“The people of Constantinople wanted nothing to do with fighting the Latins. From hindsight this seems a baffling response to the impending destruction of their city. With the hated enemy in the gates poised to destroy their homes, steal their goods, rape their women, and either expel or kill them, why did the frequently violent Byzantine population (think Nika riots) suddenly become so meek and mild? Even more amazingly, the large majority of the population did not even attempt to avoid the sack by leaving the city.”

A compelling argument is that the people lacked hindsight and “viewed events from their own history and personal experiences…There was no precedent for the final outcome…no foreign army had ever gained entry into the city.” However, there actually was precedent which the people should have been more aware of - the brutal sack of Thessaloniki. Instead, for the citizenry civil wars were “an expected part of life.” It is likely the people of Constantinople saw this more akin to a civil war due to the crusaders dangling the puppet Alexios IV Angelos.

Though they did not support Alexios IV, they did not see the actual threat for what it truly was - barbarians were at the gates and they were here to sack New Rome. “Rather than fight for the latest in a line of short-lived emperors, they chose once again to accept the crusading army’s claimant to the throne” assuming it would not be in the “new emperor’s interests to see his capital destroyed.” But they would destroy the capital of the new “Latin Empire.” 

Constantine Laskaris, brother of the future Theodore Laskaris of Nicaea, tried to rally the people of the city to fight. However, they did not, and the Varangians deserted after seeing that. The city fell with a whimper.

Source - The Fourth Crusade: The Conquest of Constantinople by Donald E. Queller & Thomas F. Madden