My father was a structural engineer who worked for the American Bureau of Shipping (a USCG chartered non-profit) whose offices were in WTC-1. He was in NJ when the attacks occured. I remember him talking me through his understanding of what was a horrible but very understandable event - from an engineering perspective. The aircraft clearly did fly into the buidling no on really doubts that. The crashes/immediate explosions themselves were insignificant compared to the intense heat of the ensuing fires, fueled by jet fuel, which changed the structural/weight-bearing properties of the steel support structures. Under heat steel (and most other materials) lose or have their weight-bearing capability significantly altered. Then as the floors above the fire began to collapse downward they effectively became pile drivers smashing into subsequent floors, increasing in energy with each collapse. None of this is really hard to understand or requires a conspiracy.
Occams Razor should rule here and, if you are interested, Popular Mechanics also did a very through treatment debunking WTC conspiracy theories over a decade ago - look for it you may find it interesting.
Trying to argue with people who get their information directly from highly-placed sources within the Mossad or FSB--or even from some clown's internet blog---is usually futile. Good try, though.