It's fairly obvious you have done very little research on these topics, otherwise you would know by now how quite improbable LIHOP would have been able to be pulled off.
The reason you wouldn't find any information on 70 full-field FBI investigations because it turned out to be a gross exaggeration. This can exemplified by the Phoenix Memo, which was a smoking gun but got buried because of the systematic failings of the intelligence community. Because of this gross exaggeration, the Bush Administration let its guard down, because as Bush himself put it, he felt assured the FBI was on top of everything when the exact opposite was true.
As far as the surveillance of federal buildings in New York, it was looked into and turned out to be Yemeni tourists taking pictures. Time magazine uncovered this even before the 9/11 commission report came out.
This type of information isn't readily available from Google University. You're going to really have to crack some books open if you are really serious about the political side of the argument. These books are all independently researched, some by Pulitzer Prize winning authors who traveled the world interviewing and researching. Here, in my opinion are the essentials (there are more of course): Ghost Wars, Perfect Soldiers, Spying Blind, Looming Tower, The Shadow Factory, The Bin Ladens, and Terror In The Name of God. Only a couple of truthers on this forum have read any of these books, and they have grossly misinterpreted the content. But if if you read these books objectively, you will see just how improbable LIHOP is, in fact, approaching impossible.
In short, 9/11 happened because of an archaic, bureaucratic system that didn't encourage sharing of intelligence. And for the most part, administrators and most agents were still locked into their old ways and never adapted to new ways to fight terrorism (for example, the head of the FBI, Louis Freeh, had his computer removed from his office in 1998).