The debris from the Twin Towers damaged the building and started the fires, but the reports state that the damage did not cause the collapse. The fires did by weakening the support girders.
"The fire expanded the girders of the building, causing some to lose their structural integrity. This led column number 79, a critical column supporting a large part of the 13th floor, to buckle, causing the floors above it to collapse to the fifth floor; however, this could not be seen from outside the building. The structure also developed cracks in the facade just before the entire building started to fall."
And:
"With a loss of lateral support across nine floors, column 79 buckled – pulling the east penthouse and nearby columns down with it. With the buckling of these critical columns, the collapse then progressed east-to-west across the core, ultimately overloading the perimeter support, which buckled between Floors 7 and 17, causing the remaining portion of the building above to fall downward as a single unit. The fires, which were fueled by office contents and burned for 7 hours, along with the lack of water, were the key reasons for the collapse."
We are not talking "small fires", as you stated:
"Over the course of the day, fires burned out of control on several floors of 7 World Trade Center, the flames visible on the east side of the building.
[35][36]:4 During the afternoon, the fire was also seen on floors 6–10, 13–14, 19–22, and 29–30.
[31]:24 (PDF p. 28) In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon.
[7]"
What about any evidence for demolition?
"The NIST report found no evidence supporting the conspiracy theories that 7 World Trade Center was brought down by controlled demolition. Specifically, the window breakage pattern and blast sounds that would have resulted from the use of explosives were not observed."
Wiki source
So, why should I ignore all this in favor of "well, it looks like a demolition"? Besides having no evidence, It still suffers from my previous criticism: What of other modes of destruction can also appear like a demolition?