It wasn't anyone's "fault" per se -- the city grew wildly for a long while, completely unplanned, and Senators and other posh folks from the three dozen or so families which ran everything and owned a lot of it rebuilt burned areas in brick. The fact that this one survives to this day shows they knew what they were doing.
Until the Great Fire that occurred during the reign of Nero, much of the city was still pretty shaky as far as construction and flammability. The firefighting crews instituted by Crassus fought that fire.
Most of these Roman apartments didn't have kitchens, which reduced the number of house fires. That also led to a take-out food culture, and much healthier snacks (fruits, nuts, greens) around the house.
It should be noted also that Cicero, the Roman equivalent of an ambulance chaser, owned a bunch of apartment buildings.
This is why Rome only has two subway lines. You can’t dig to plant tomatoes (much less a rtain tunnel) without hitting historic ruins.
They’ve cleaned the place in the video up. Last I was there all of that structure that could be accessed from the sidewalk was covered in hand bills.
A couple of hundred yards to the left of that spot (north, directly in front of the wedding cake) is one of Rome’s best free attractions, the world’s most theatrical traffic cops.
https://www.youtube.com/watch?v=zExVyA2rX6c