After the intelligence failures became evident post 9/11, there was much debate on how to improve things. The President's proposal (as opposed to what the government janitor says above) was to create a cabinet level position that would act as communications liaison between the various intelligence and law enforcement agencies. Theoretically, this would remedy the situations where items of concern, say at the FAA, would be readily available to the FBI.
This did not satisfy the Democrats, who were in control of the Senate at that time. They raised a fuss, stating that this was too important of a task to just have a communications officer in charge of. Because of their protests, Bush performed a major flop, abandoning his initial proposal and, with the cooperation of the Senate, created the Department of Homeland Security, an all-encompassing agency which was supposed to consolidate the various agencies under one big umbrella.
In conjunction with this effort, the topic of airport security also was a big item. The Republican proposal was to increase FAA oversight and training requirements for the contract security forces already in place at most airports. This, again, did not satisfy the Democrats insatiable appetites for making everything a big government agency, so the TSA was born, federalizing all airport security in the mistaken notion that doing so would suddenly turn fairly low paid, semi-effective contract security personnel into fairly low paid, super security officers extraordinaire.
If you've been paying attention lately, you'd have noticed that the government is now experimenting with contracting security operations at several airports because the TSA employees had proven no more effective than the old contractors. But they are much more expensive.
So, to sum up, Homeland Security and TSA, technically Bush creations since he signed the bill, are actually constructs of the traditional Democratic desire for large government agencies controlling all facets of our lives.