Thats a good question. What did we learn?
We learned there were Israeli intelligence agents documenting the attack against the WTC. They danced and celebrated the strike. This is why they are known as the dancing Israelis. They were arrested and sent back to Israel.
If they knew the attack was coming, Israeli politicians knew. The question is if they told their GREATEST ALLY about it. If they didn't, that's bad, if they did, that's even worse.