He may have left the car in the paid garage, because he didn't have protected parking at home. Didn't want to have to move the car every few hours to accommodate parking regulations. Friends in the city keep their car in a similar place, getting it out only for special occasions. Use public transportation or hitch rides everywhere else. Particularly if parking is difficult at their destination.
There has to be a reason why he'd leave a car there and get a ride to New Castle. And that would mean there would be someone else he encountered on the evening of Dec 28, someone who took him from the train station to New Castle and we haven't yet heard from.
Depending on the degree of foul play, there are various possibilities. This might be a taxi. It might be the driver of the DART Route 15 bus. This might be a car-pooling arrangement. This might be a "Good Samaritan" who "helped" him out...taking him to New Castle, knocking him on the head, and setting the fires.
The blaring TV might be an unintentional red herring, if he unintentionally left it so it came on loudly while he was gone. Or someone who likes to have loud TV 24 hours a day was waiting for him to return. All depends on what you consider reasonable possibilities.