(1) Larry Silverstein is not the sole owner of the WTC. He is merely the CEO of an enormous consortium of investors.
(2) So far the WTC has been an enormous LOSS to this consortium because its lease requires it to make very large payments to the Port Authority (the actual owner) - even though the consortium has been unable to collect a penny in rent since Sept 11th.
(3) If any of those nasty rumors trying to connect Silverstein with the attack were true, you'd think they'd be advanced during the very pricey lawsuits that the consortium has had to bring. First there was an enormous lawsuit against, primarily, the Lloyds of London insurance consortium, which had tried to argue that it could pay off only for one mishap for the entire loss of the whole WTC, on the pretext that the collisions into two towers were part of only one conspiracy and therefore only a single mishap. You'd think if Silverstein knew what was going to happen, he'd have had the insurance policy written a lot more clearly on that issue. Now his consortium is suing airlines for millions - if there were anything to those nasty rumors, you can be sure the airlines will mention them rather than have to pay millions of dollars.