I think that the evidence was planted, so they could put Saudi Arabia under political pressure.
Especially now when the oil-dollar contract is ending, the US needs to threat them.

The "hijackers" who drank alcohol and went to parties (on Ramadan), were connected to Saudi Arabia. And that is why the US invaded Iraq and Afghanistan. While Bin Laden was in Pakistan. Bin Laden hated the US for their foreign politics.

What is 911 truth:

Architects and Engineers for 911 truth:
Based on the physical evidence, the planes did not bring down the 3 WTC towers. It is physically impossible.
There is too much energy that goes both to the free-fall, to the destruction of the steel-core building, and to the explosive like side-ways expelling of heavy material. The extra energy proofs that we have a demolition.
This additional energy was added via explosive chemicals, including thermite. The chemical residues of thermite were present in the dust. And the thermite was burning for weeks under water even after everything was down.
All evidence of the chemical affected steel structure was removed quickly and shipped off to China via a prepared transport.

Pilots for 911 truth:
The "hijacked" planes were flying faster and more agile than a normal passenger plane.
And from the remains (like engines) they can be identified as the military version of that plane.
Especially the circling down towards the pentagon is extremely hard, even for a normal pilot with a normal plane.
The switch had likely taken place when the transponders of 4 planes were switched off in region that was outside radar vision.
The military was also doing hijacking exercises at the same time and the day before, causing a chaos at the control towers.
As they were thinking that the hijacking were related to the exercises.
The hijacking simulations likely included recorded messages to make it seem more real.

Firefighters for 911 truth:
The fires were already going out when the preparation phase started.
During the preparation, explosions could be heard all over the building.
They were targeting the steel core of the building.
Then later, the demolition phase started.
And explosions turned many firefighters into little peaces of meat that were spread around.
Some of it landed on top of other buildings, and these fire-fighters could be DNA identified later.