No, there is no reason to believe that the US government was involved in the 9/11 attacks.

The science behind the destruction of the buildings is clear. There were no missiles. There were no demolition charges. The airliners, and the resulting fire, destroyed the towers.

The towers were designed to survive the impact of an airliner. And in fact they did. Where the design failed was in resisting the fire that followed the impacts. The contents of a modern office are mostly flamable. In fact, much of it is fuel. Plastics are made from oil. And can have as much as 3 times the fuel content per pound as coal. And these days plastics are everywhere. Next time you are in an office, look at everything and note what they are made of. Plastic, paper, wood. So you had a very intense fire igniting pretty much every flamable object on several floors of the towers. All the glass was blown out, so the wind could whip through cleanly to feed the flames. And the fire suppression design of the towers failed because it was not sufficiently protected.

What that adds up to is a blast furnace. You know how a blacksmith heats a horseshoe in order to make it malable. Heat steel enough and it loses its strength. It becomes malable and bendable.

This is what happened. The phisical structure of the towers that survived the impacts were critically weakened by the resulting fire. Until they simply were no longer stong enough to hold the vast weight of the towers up. As each floor collapsed down on top of the ones below it, that vast weight shattered the concrete and broke the steel as it hit. And it did that floor after floor all the way to the ground.

As to the fact that many people beleive that the government, did it: So what? Many people have beleived false things before. This is no different. It isn't at all relevent to what happened.