The Navy's decision to fight for the aircraft might not have been based on the aircraft itself. The Navy has a compelling interest in keeping rights to all salvage that was once (still is) Navy property. If somebody lays claim to a US Navy ship sitting on the bottom of the ocean, the Navy will immediately assert their legitimate claim. If they let a few people keep small pieces of Navy property, including an old, demolished airplane, it might set precedent for such salvage.
I'm not up on maritime/salvage law, but their approach appears to be similar to patent copyright law; you must aggressively defend your patents and copyrights or risk losing them.
BTW; I'm glad the guy won. I'd hate to see the aircraft decaying in a swamp or the guy's hard work lost.
No, whether as to salvage or patent or copyright law, although failure to assert a claim as to a particular thing can cause a lapse of the claim as to that thing, that does weaken potential claims as to other things.
In other stories, the Navy admitted that they wanted the aircraft for its value as a museum holding.
Didn't think of that. Imagine if somebody wanted to salvage the Lexington or Yorktown. The German Prinz Eugen survived an atomic test to capsize on a reef and it might still be accessable.
If they raise it and float it, why the hell should the Navy care ?