If you start by assuming that the destruction of WTC7 (which was hardly "one of the most important buildings in NY, BTW) was planned, then every event leading up to it can be characterised as "convenient", and the fact that it led to the destruction put forward as evidence that the destruction was planned. However, it's a circular argument, because your identification of prior events as evidence of planned destruction is itself contingent on the acceptance of the assumption that the destruction was planned. If you start out without the assumption that the destruction was planned, there's nothing a priori suspicious in isolation about the fact that a specific event or condition contributed to the collapse.