If you were to go off simple physics, the buildings should have fallen over, not straight down. The collapses were way to perfect. These are arguments that can go on for eternity. Thing is, YOU only know what THEY want you too.
I'm curious why you think the buildings should have fallen over?
Their design included a core up the middle of each building. When they collapsed the top did "fall over" above the impact, but the lower floors pancaked straight down like the building was designed to do.