I'm no expert in structural engineering, but some experts have claimed that there was thermite in the buildings, a substance used in demolitions. If you look at the video, there are certain trademarks to how the buildings came down, similar to demolitions. But the real giveaway, IMO, is Building 7, the one that was brought down hours after the attack. The media first reported that 7 had structural deficiencies and could collapse, something not true due to how the building was situated around the Towers. But later the media and the building owner admitted that they were going to bring down 7, specifically for the purpose of safely destroying a building that would eventually collapse. The problem is that it takes days, but most probably more than a week, to safely set the charges to successfully orchestrate a controlled demolition of a building of that size. People have to realize that professionals had only about 6 hours to work with after the planes hit to set up the charges. That's not enough time.
All of the surrounding buildings next to the twin towers did not collapse or needed to be demolished, but yet this one building did despite not being directly adjacent to Ground Zero. Just for disclosure, B7 housed offices of Arthur Anderson, the defunct Enron buddies, along with some investment bank offices and FBI/CIA substations. But these facts don't really matter.
I don't understand why these supposedly "sane, non-conspiracy theorists realists" don't even call for more investigation. I understand why they might not believe what I have to say, but if they read the 9/11 Commission Report, they should at least acknowledge that more investigation would be a good thing, but they don't. They want to brush it under the rug.