What exactly does 'It's all academic' mean when referring to the closing moments of a sports game? You'll often hear 'This one's academic!' or 'It's all academic from this point forward' or 'It's all academic.' Does it mean anything, or is it purely meaningless jargon?
The French say fait accompli to indicate a presumably irreversible deed or fact. Competitors in a sporting event play out a game to the bitter end because the "rules" say they should. Rules--the theory, if you will--comprise the "academic" part of the saying "It's all academic."
In our baseball exemplar, you might invoke the tautology "rules are rules," which is a way of saying there is no sense protesting the premature ending of a ninth-inning fiasco, even though it might be the sensible, humanitarian thing to do. Why? Because rules are rules. In other words, it may be obvious at some point as to who is going to win, but the rules say the game ends only after the third strike of the third out of the last batter at the bottom of the ninth.
As for academic discussions on a question once considered controversial but considered settled now for years, all such discussions are said to be purely, or merely, academic. Why? Well, despite the question's having become passe, unimportant, or even irrelevant, sometimes people just love to hear the sound of their own voices!
Though the information can be found on the internet, it's not obvious where to find an explanation of the exact sense (polyseme) of academic you mention. My first port of call, googling "academic" + "meaning", then using the link to thefreedictionary.com, wasn't as helpful as it usually is.
At the link to dictionary.reference.com, however, one soon finds: (bolding mine)
3. theoretical or hypothetical; not practical, realistic, or directly useful:
an academic question; an academic discussion of a matter already decided. .
There has almost certainly been a drift towards the metaphorical sense from the original, via 'purely academic' and perhaps 'merely academic'.
It's the bottom of the 9th inning, the Yankees are winning 15 to 0, and the other team's at bat. The sportscaster says "It's all academic now" because there's an almost zero probability that the team at bat is going to score 15 or 16 runs and tie or win the game.
"Academic" refers to formal study. Formalities are motions that people go through because they have to, whether they want to or not. They're often meaningless. Playing the last three outs at the bottom half of the 9th inning in this game is strictly a formality. The Yankees will certainly win and the other team will certainly lose. But no one can stop the game because the 15-0 gap is too large to overcome. That's why spectators at sporting events frequently leave before the game's over, despite Yogi's wise observation that "It ain't over till it's over". I've seen at least one game in which a team scored 10 runs in the bottom of the 9th and won the game in front of a half-empty stadium. It was a long time ago.
It's not meaningless jargon; rather, it's resignation, defeatism, and pessimism. It's understandable, of course.