WTC-7 falling is a fact, not a theory.
The reason why it fell is a theory.
Yeah, the controlled demolition theory?

This is an article from 2017, but this was covered and discussed many times many years ago.
https://www.popularmechanics.com/technology/design/a3524/4278874/As a structural engineer, I too was surprised at how WTC 1 and WTC 2 pancaked like they did. However, after forensic reports detailed how the blast degraded the fireproofing as well as the jet fuel igniting fires inside the structure that designers could not have anticipated, that explained a lot. It's not unlike progressive collapse due to blast. Those buildings are designed for fires from office materials, not what they experienced on 9/11.
As for WTC 7, the collateral damage and fires did similar and the fire sprinkler system failed. The collapse started some 7+ hours after the fires started. Life safety standards are to ensure people can safely exit the building, not to ensure they remain operational or even standing after the design event. Be it fire, earthquake, wind, etc.
Well, I guess findings can be fudged, but not from studies of that many independent consulting firms that studied the event.