I think WTC7 is very indicative of the lingering antisemitism in alot of the Truthers' mind (maybe not a full-fledged holocaust denialism in most, but indeed some inclination to believe that the Jews are somehow responsible when it comes to world events).
This is how I see a newcomer Truther's mind at work:
We have a building which fell six hours after the WTC collapse.
This event is somehow strange, since the building wasn't hit by a plane and that it wasn't reported extensively by the media (which is an honest doubt most people will have when they first learn about it).
If you look into it further, most people will find that the building suffered massive damage from the collapse of the two WTC towers and that nobody was killed in its collapsed, therefore not worthy of much TV coverage as it is peripheral to the terrorist attacks.
These people will then move on with their lives.
But alas, some will find the visual similitude with controlled demolition more convincing than the NIST prelim report and multiple eye witness testimonies and will then proceed with more research (i.e: conspiracy sites). This lingering doubt may have something to do with their own preconceived distrust in their government (Jews? Not just yet...).
While doing their "research", they will find out that the owner of the said building is of the Jewish faith (or most will come to that conclusion because of his name) and then they will learn that he said in a television interview that he said to "pull it". Of course by that he meant to pull the firefighting operations in the burning building but the new found Truthers will believe that he ordered this building to explode. Why is that? I think it's at this point a confirmation for most Truthers that 9/11 was an inside job.
After all, he is Jewish and America supports Israel...
You see, we only had a building that collapsed to start with, and now we have a massive Jewish conspiracy.