That skyscraper alone could accommodate thousands of people living and working there at the same time. If it collapsed, the consequences would be unimaginable.
Besides, the financial district near the river had loads of skyscrapers. If one collapsed, it might end up crashing into other buildings and create a chain reaction. No one could calculate just how many innocents would end up dead.
Fortunately, before the creature completely ate up the foundation of the building, it was discovered by an observant superhuman.
Since he strengthened the foundation in time and sent the people away, the attack did not result in any deaths.
But since a lot of time was wasted on saving lives, the attacker was able to escape through the complicated underground maze.
The city was not that lucky during the attack three days later.
At that time, it was the peak hour when everyone went to work or got off work.