Ken, I disagree with you on Bowden, though I can't really explain why. Just a feeling that he's not afraid to pull the trigger on a big deal, if a half-decent one comes along.
Thing is, he may not get a good enough deal to make, and he'll be criticized for doing nothing. In some cases, you're damned if you do, and damned if you don't.
Plus Bowden's whole reputation is of a guy with an itchy trigger finger who will trade just about anybody anytime in the season.
I agree with tomterp that its more a combination of a lack of tradable players. Look at the guys who you would have just about bet would be traded who are on the DL: Sledge (or another OF if he had played great in April), Rauch, Spivey. Plus all the guys who were on the DL at a time when Bowden might have pulled off a trade for them. We all remember Day-Encarnacion but who knows if Bowden had plans to trade Vidro B4 the trip to the DL, Nick (same), Wilkie (vague forearm nerve problem which may scare away bidders) or Armas.
Other thing is money. I have zero doubt that is MLB had gotten ownership in place by the deadline we'd be seeing one of those "star player for prospects and an undisclosed amount of cash" deals.
Final thing is actual MLB restrictions on him. I dunno if they have told him he can't trade "stars" or what stars the Nats have, pending new ownership and has to regard himself as the Nats steward, not permanent GM.