While the white hot glare of the public spotlight was on him, he may have been too pinned down to act, but after that spotlight swung away on 9-11, when he already knew that DC cops were finished with the park searches and that the only risk of discovery of the body was by some joker with a dog, a highly foreseeable event in an urban park, it would have been in his interest to remove Chandra's body and clothes. He didn't have to clean the scene perfectly. He just had to get the gross evidence of a crime out of there, so that even if a dog did alert on some residual odor, the dog's owner would see nothing amiss.
As for choosing to dump a body there --- again, a crowded urban park --- after committing the crime somewhere else, I disagree again. Why would someone drive to a city park to dump a body when there are hundreds of places within an hour's drive of Washington which are more suitable? If the killer had the time to move the body, surely he had the time to take her out to the woods in Maryland and bury her. I think it's far more plausible that her body was found there because she was killed there.
There is one circumstance that may have made it difficult for him to act. If the Levys were watching him, or he thought they might be watching him, he may have felt that it was too dangerous to return to the scene of the crime. That is only reason I can think of to explain why Gary Condit, if he murdered this girl and left her on public ground in a public park, would not have gone out there at some point post 9-11 and removed the evidence.
If the Levys were watching him, or he thought they might be watching him
Do believe it's the FBI that's watching him. Remember Anne Marie Smith was called in by SF agent (On order of DC) just days after CHandra's parents reported her missing. The watch box was dumped not because he was afraid that the tabloid were going through his trash. It was the FBI! The FBI sort of "volunteer" to help the DCPD.
As regards the deterrent effect on Condit of the possibility that he might leave forensic evidence on the body, well that is a very good argument for believing that murder is impossible. The 20,000 murders that occur every year in the United States alone are obviously just a figment of our collective imagination.