What appears to have possibly happened here, by virtue of the fact that they appeared to have such high hopes, is that they let up on the battle and effort banking on what they were told by those they were in contact with. Who may have been mislead themselves.
I've seen this pattern before and in fact I've used it against adversaries (not in the patent area obviously). And it was used against me (which I'm guessing is where I learned it in the first place.)
You allow the other side to think they are going to win and so they end up easing up just a bit on the effort because in their mind they think they have pretty much either won the battle or have come real close to winning. (Isn't this also done in sports?)
I learned this lesson early on in business (out of college) when I lodged a complaint against the electric company for pulling the power to some machinery. The electric company immediately told me I was right! And that they would, in so many words, compensate me for the lost profits and the like (not that exactly but close enough it was a long time ago).
As time dragged on they still mildly assured me that they were going to do something. After perhaps 6 months past and I drew a line in the sand (all this dating is from memory btw.) At that point they finally just told me they weren't going to do anything and "well to bad sorry".
But by that point I had lost my initial anger and steam and just decided to forget about it.
Had they told me from day one (or week one) that they didn't agree I would have approached the situation much differently and mounted a different strategy. I didn't have a strategy because, well, I didn't think I needed one.