We all want hard and fast rules for this, but it comes down to judgment calls. And we all seem to be afraid of making judgment calls. I don't know much about League of Legends, so I might be off base here, but the original question seems pretty broad. The possible duplicate is pretty narrow. I'm going to try to talk about the general case of narrow vs broad here, and not the LoL question specifically, because as I said, I don't have the LoL knowledge to know where this specific example falls.
I do not believe we should close narrow questions as duplicates of broad questions unless there is a reasonable expectation that a decent answer to the broad question would cover the narrow case.
Note that whether or not an answer already exists to the broad question is irrelevant. It comes down to whether or not you have a reasonable expectation to assume the broad question pretty much requires the other question's info in an acceptable answer. Which is why this comes down to a judgment call, which a lot of people here seem uncomfortable with. We always seem to want a hard and fast rule, even when it is to our detriment.
In this particular case, not knowing much about League of Legends, I don't know what a reasonable expectation would be. For those of you familiar with it, would you have expected an answer to the broad question to have covered the duplicate question? If so, okay, let the duplicate closure stand. If you wouldn't have expected it until you saw the "dupe" asked, though, we're creating a bad situation in which the original question didn't really have a reasonable expectation of covering what was asked until after someone requested more details (via a separate question). Then people look at it, say "Oh, you know what, this broad question over here could kind of cover that, though really there's no expectation that someone will unless a bounty gets posted", and it gets closed as a dupe. What service are we doing to anyone by forcing some narrow details into a broad question? We're creating a situation in which someone is unlikely to get an answer. We're also creating an expectation that answers to broad questions should be all-encompassing, including nitty-gritty details that many people may never care about. That's bad. I mean, if an answer wants to cover that, great! But expecting it turns the Q&A format into a Wiki format.
Lastly, I really disagree with the idea that a user should be required to post a bounty to get their question some initial attention.